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Grigoras Law · Toronto · Las Vegas · Litigation Saturday, 25 April 2026
Economic Torts

Civil Conspiracy.

Legal usage · from conspirare, "to plot or act in harmony" An agreement or combination between two or more persons to act together for the purpose of causing harm to another, whether by lawful or unlawful means, resulting in actual damage. A tort when the conduct leads to loss or injury.

Grigoras Law represents plaintiffs and defendants across Ontario in civil conspiracy matters involving coordinated conduct designed to cause economic harm. We handle claims in both unlawful means and lawful means (predominant purpose) conspiracy, and the multi-party commercial wrongdoing that frequently sits alongside them.

What we do

Civil Conspiracy services.

Our work falls into three registers: building claims for plaintiffs, defending claims brought against clients, and handling the procedural complexity that conspiracy actions tend to attract. The items below are representative. Each links to a longer writeup.

Representative work

Selected matters.

Matters below are representative of civil conspiracy work the firm has handled. Identifying details have been generalized. Case results vary. Past outcomes do not predict future results.

ON SCJ Cannabis sector

Multi-party cannabis investment fraud conspiracy

Represented investor in an action against multiple corporate and individual defendants accused of conspiring to defraud through misrepresentations about cannabis cultivation facilities. Claims included unlawful means conspiracy, corporate veil piercing, fraudulent misrepresentation, and oppression remedy. Case involved alleged diversion of investor funds and coordination among family-controlled entities to defeat creditor claims.

Investment Fraud
ON SCJ Real estate & family business

Real estate development conspiracy and fraudulent conveyance

Represented plaintiffs in an action against defendant accused of conspiring with a controlling shareholder to strip assets from development companies through fraudulent transfers. Claims included civil conspiracy, conversion, breach of fiduciary duty, and corporate veil piercing. Case involved orchestrated transfers of real property and corporate funds to defeat outstanding creditor claims.

Fraudulent Transfer
The law, explained

A practitioner's guide to civil conspiracy in Ontario.

Long-form analysis of the doctrine: its historical development, the elements of both varieties, the defences, and the litigation strategy that shapes how these files are actually run. Written as a reference. Updated periodically.

Chapter One

Understanding Civil Conspiracy.

What the tort is, where it came from, and why Canadian courts have kept it narrow.

What is Civil Conspiracy?

Civil conspiracy is a common law tort that holds multiple parties liable when they agree to act together in a way that causes economic harm to another. The term derives from the Latin conspirare, meaning "to breathe together," reflecting the core concept of coordinated wrongdoing. Unlike other economic torts, conspiracy requires proof of an agreement between two or more people. Acting alone, the same conduct might not attract liability.

What makes conspiracy unusual is that it is not simply joint tortfeasance. As the UK Supreme Court explained in JSC BTA Bank v. Ablyazov[2015] UKSC 64. Confirms conspiracy as a distinct tort with primary liability., conspiracy is a distinct tort with primary liability. The fact of combination can alter the legal character of acts that would be lawful if done individually. In other words, plurality itself can convert otherwise permissible conduct into tortious conduct.

Canadian courts recognize civil conspiracy as an established cause of action, though its scope and rationale have been subject to judicial scrutiny. The tort protects against coordinated economic harm, whether inflicted through lawful or unlawful means, and serves as a check on concerted conduct designed to injure business interests.

Historical Development and Purpose

Civil conspiracy has medieval origins. It began as an action providing civil redress where two or more persons combined to abuse the court's criminal process. Over time, the writ evolved into an action on the case and flourished in the nineteenth century, largely as a judicial tool to regulate activities by organized labour and rival entrepreneurs.

The tort developed differently in Commonwealth jurisdictions than in the United States. American courts remained skeptical of the premise that mere numbers could convert lawful conduct into unlawful conduct. Many U.S. jurisdictions rejected civil conspiracy entirely or adopted it only in narrow forms. Instead, American law developed independent doctrines such as unfair competition and the prima facie tort doctrine, which provide courts with broader remedies not dependent on combination.

To suggest acts done by one street-corner grocer in concert with a second are more oppressive than acts by a chain of supermarkets under single ownership is to ignore modern economic realities. Lord Diplock · Lonrho Ltd. v. Shell Petroleum Co. (1981)

In contrast, English and Commonwealth courts embraced conspiracy to regulate industrial and commercial disputes and to reinforce laissez-faire economic principles. The classic articulation came in Mogul Steamship Co. v. McGregor, Gow and Co.(1889) 23 QBD 598 (CA), aff'd [1892] AC 25 (HL)., where Bowen L.J. explained that combination may make "oppressive or dangerous that which if it proceeded only from a single person would be otherwise."

The House of Lords in Lonrho Ltd. v. Shell Petroleum Co.[1982] AC 173 (HL). questioned this foundation. Lord Diplock observed that modern economic realities cannot be ignored. Nevertheless, the court retained predominant purpose conspiracy because it was too deeply embedded in precedent to be reversed. Canadian law followed a parallel evolution. The Supreme Court of Canada in Canada Cement LaFarge Ltd. v. British Columbia Lightweight Aggregate Ltd.[1983] 1 S.C.R. 452. The leading Canadian authority on unlawful means conspiracy. acknowledged conspiracy as a judicial anachronism but concluded it was too late to uproot it from the common law.

Two Varieties of Conspiracy

Modern Canadian law recognizes two forms of civil conspiracy, terminology clarified by the Supreme Court in Pro-Sys Consultants Ltd. v. Microsoft Corp.2013 SCC 57, [2013] 3 S.C.R. 477.:

  1. Predominant Purpose Conspiracy: Liability arises when two or more persons agree to engage in conduct (lawful or unlawful) where the predominant purpose is to injure the plaintiff, and damage results. The tortious quality stems from the fact of acting together with this malicious purpose, not from the means used.
  2. Unlawful Means Conspiracy: Liability arises when two or more persons agree to engage in unlawful conduct directed at the plaintiff, injury is foreseeable, and damage results. Here the tortious quality stems from both the unlawful means and the fact of combination. Injury need not be the predominant purpose, but there must be at least constructive intent to harm.

The distinction is crucial. Predominant purpose conspiracy can be committed using entirely lawful means, provided the conspirators' main objective is to harm the plaintiff. This is an anomaly: it makes combination itself wrongful when accompanied by malicious intent. Unlawful means conspiracy, by contrast, requires unlawful conduct but does not require that harming the plaintiff be the main objective.

Chapter Two

Elements of the tort.

What plaintiffs must prove, element by element, for each variety.

Predominant Purpose Conspiracy Elements

To succeed in a claim for predominant purpose conspiracy, the plaintiff must prove:

  1. An agreement between two or more persons to engage in conduct (whether lawful or unlawful);
  2. The predominant purpose of the agreement is to injure the plaintiff; and
  3. The plaintiff suffers damage as a result.

This form of conspiracy is unusual because it renders otherwise lawful conduct actionable based solely on the conspirators' malicious intent. The rationale is that coordinated action motivated by a desire to harm, rather than to advance legitimate interests, is inherently wrongful.

Unlawful Means Conspiracy Elements

To succeed in a claim for unlawful means conspiracy, the plaintiff must prove:

  1. An agreement between two or more persons to engage in conduct;
  2. The conduct is directed at the plaintiff (alone or together with others);
  3. The means employed are unlawful; and
  4. The defendants should know in the circumstances that injury to the plaintiff is likely to result, and damage does result.

As articulated in Canada Cement LaFarge, this form requires "constructive intent" to injure. The defendants must have known or ought to have known that their unlawful conduct would harm the plaintiff. Predominant purpose to injure is not necessary, but the unlawful means must be directed toward the plaintiff, not merely incidental to some other objective.

Chapter Three

Predominant Purpose Conspiracy.

Agreement, purpose, and damage: the three elements unpacked, with the evidentiary requirements at each stage.

Agreement Between Two or More

The foundation of conspiracy is an agreement. As stated in Mulcahy v. The Queen(1868) LR 3 HL 306., "a conspiracy consists not merely in the intention of two or more, but in the agreement of two or more." The agreement constitutes a joint plan or common design and need not amount to a legally enforceable contract.

Individual defendants are liable only if they intentionally participate in the agreement. Mere knowledge of or acquiescence in the conspiracy is insufficient. Making an agreement is not the same as simply "being in agreement." Directors who all vote the same way at a meeting are not thereby conspiring unless they entered into a compact in advance.

Although direct evidence of an agreement is preferred, conspiracy can be established by inference from circumstantial evidence, provided the facts cannot fairly admit any other reasonable explanation. The law recognizes that conspirators rarely document their schemes. Evidence of parallel conduct, coordinated timing, common interests, and communication between alleged conspirators may support an inference of agreement.

An overt act in furtherance of the agreement is required. Unlike criminal conspiracy, the civil tort is not complete until the conspirators take steps to execute their plan and damage results. Pleadings must specify the overt acts and attribute them to the appropriate defendants. Corporations can be parties to conspiracies, and a company can conspire with its directors since a corporation is a separate legal entity.

Purpose to Injure the Plaintiff

The leading authority on this element is Crofter Hand Woven Harris Tweed Co. v. Veitch[1942] AC 435 (HL). Leading authority on the predominant purpose test.. In that case, union officials instructed dockers to refuse handling the plaintiff's yarn, causing economic loss. The House of Lords held the conspiracy was not actionable because the predominant purpose was promoting the union's legitimate self-interest, not injuring the plaintiff.

Several principles emerge from Crofter and subsequent cases:

  • The test focuses on the true purpose or object of the combination, not the natural or probable result of the defendants' actions.
  • "Object" means the ultimate end or goal. It is distinguished from "motive" or "immediate purpose."
  • Where multiple objects exist, liability depends on the predominant object.
  • A conspiracy whose predominant object is to injure the plaintiff is unlawful.
  • If the predominant object is to advance the conspirators' legitimate self-interest, the combination is lawful.

The burden of proof lies with the plaintiff to establish the unlawful object. Courts examine the defendants' actual purpose, which may be inferred from their conduct and the factual circumstances. Defendants whose primary aim is self-advancement do not commit this tort merely because they foresee harm to a competitor.

Damage to the Plaintiff

An agreement with a predominant purpose to injure is not itself actionable. The defendants must perform overt acts pursuant to the agreement that cause actual damage to the plaintiff. Damage is the gist of the civil action for conspiracy. Without it, no tort is complete.

The weight of authority suggests pecuniary loss is required at least in commercial conspiracy cases. Once established, damages are at large in the sense that specific quantification of each element of loss is not necessary. Aggravated and exemplary damages may be awarded where the conduct warrants such relief.

Chapter Four

Unlawful Means Conspiracy.

The variant that captures coordinated wrongdoing by otherwise lawful actors, where the means themselves are tortious.

Means Directed at the Plaintiff

The Supreme Court of Canada fundamentally reshaped unlawful means conspiracy in Canada Cement LaFarge. The defendants were major cement producers found to have violated competition law by conspiring to drive out competitors. The plaintiff, a supplier of aggregate to the cement industry, claimed damages.

Although the defendants' conduct was clearly unlawful, the Supreme Court held no liability existed because the conspiracy was not directed at the plaintiff. The defendants' anticompetitive agreement targeted consumers by keeping concrete prices high. Any harm to the plaintiff, an aggregate supplier, was collateral and incidental, not part of the conspiracy's objectives.

Justice Estey formulated the modern Canadian test: unlawful means conspiracy requires that the unlawful conduct be "directed towards the plaintiff" and that "the defendants should know in the circumstances that injury to the plaintiff is likely to and does result." This imports a requirement of constructive intent to injure, derived from the fact that defendants should have known injury would ensue.

The Unlawful Means

"Unlawful means" has different definitions across economic torts. The Supreme Court of Canada observed in A.I. Enterprises Ltd. v. Bram Enterprises Ltd.2014 SCC 12, [2014] 1 S.C.R. 177. that there is no general requirement of consistency. In unlawful means conspiracy, the term is broader than in the tort of causing loss by unlawful means, where actionability by a third party is required.

Unlawful means in conspiracy includes:

  • Independent torts: inducing breach of contract, interference with contractual relations, nuisance, intimidation, defamation, and other actionable civil wrongs.
  • Breach of contract: while debated, breach of contract may constitute unlawful means, particularly where it interferes with the plaintiff's economic interests.
  • Criminal offences: breach of the Criminal Code, including extortion, fraud, and other indictable offences.
  • Statutory violations: breach of regulatory statutes even where no private right of action exists, such as labour relations legislation or competition law.
  • Contempt of court: as held in Ablyazov, breach of court orders can constitute unlawful means despite being penal in nature.

Framing a claim in conspiracy offers advantages: it may capture instigators who did not directly participate in the tort, it may support aggravated damages, and it provides evidentiary benefits (statements by co-conspirators are admissible against all).

Chapter Five

Defences & strategy.

What defendants can assert, and how conspiracy files actually run.

Statutory & Justification Defences

Several Canadian provinces have enacted legislation excluding civil actions against unions or their members for interference with contracts or trade arising from lawful strikes, picketing, or labour disputes. These provisions offer an effective defence to conspiracy claims in the labour context. For example, British Columbia's Labour Relations CodeRSBC 1996, c.244, s.66. specifically excludes liability for petty trespass, interference with contractual relations, or interference with trade arising from lawful strikes or picketing.

In predominant purpose conspiracy, advancing legitimate self-interest is not technically a "defence" but rather negates an essential element of the tort. If the defendants' predominant purpose was to further their own lawful interests rather than to injure the plaintiff, no unlawful object exists and the tort is not made out. Self-interest encompasses trade and business interests, union interests, and potentially other legitimate objectives.

In unlawful means conspiracy, justification is not available as a defence. The Supreme Court in Canada Cement LaFarge confirmed that once unlawful means directed at the plaintiff with constructive intent are established, the fact that defendants' predominant purpose was self-advancement does not excuse liability.

The doctrine of ex turpi causa non oritur actio (no action arises from one's own wrongdoing) may defeat a conspiracy claim by a participant in the conspiracy who later suffers injury. A party who participated in a conspiracy cannot subsequently claim damages arising from that participation.

Litigation Strategy

Civil conspiracy claims require careful evidence gathering to establish each element. Unlike single-party torts, conspiracy demands proof of coordinated action, which is rarely documented explicitly. Plaintiffs must build their case through direct and circumstantial evidence.

Agreement: Direct evidence (written agreements, recorded conversations, testimony from participants) is ideal but rare. More commonly, plaintiffs rely on circumstantial evidence: parallel conduct by alleged conspirators, meetings or communications between them, common financial interests, coordinated timing of actions, and patterns suggesting a common plan.

Purpose or intent: For predominant purpose conspiracy, plaintiffs must prove the defendants' true objective. For unlawful means conspiracy, constructive intent must be shown: that defendants knew or should have known their unlawful conduct would harm the plaintiff.

Causation and damages: Plaintiffs must prove the conspiracy caused their loss. Financial records, lost contracts, expert testimony on market conditions, and evidence of the plaintiff's business trajectory before and after the conspiracy are typical.

Conspiracy claims often arise alongside other economic torts. Counsel must consider whether to plead conspiracy alone or in combination with inducing breach of contract, interference with economic relations, defamation, intimidation, or causing loss by unlawful means. Each tort has distinct elements and advantages.

Advantages of pleading conspiracy:

  • Captures multiple defendants in a single cause of action
  • May hold liable instigators and planners who did not personally commit overt tortious acts
  • Aggravated and punitive damages may be more readily available
  • Evidentiary advantages (co-conspirator statements)

Pleadings must be specific. Courts require plaintiffs to identify the alleged conspirators, describe the agreement with particularity, specify the overt acts committed in furtherance of the conspiracy, and attribute specific acts to specific defendants. Vague or conclusory allegations may be struck out.

Early legal advice is critical. The tort's subtleties, particularly the distinction between the two varieties and the interplay with other economic torts, demand strategic thinking from the outset. Whether to pursue interim injunctive relief, how to preserve evidence of the agreement, and whether to join all potential conspirators or proceed against a subset are threshold decisions that shape the entire litigation.

Common questions

Frequently asked.

Quick answers to questions we hear most often. For anything specific to your situation, an Intake Form is the right next step.

Disclaimer. The answers provided in this FAQ section are general in nature and should not be relied upon as formal legal advice. Each individual case is unique, and a separate analysis is required to address specific context and fact situations. For comprehensive guidance tailored to your situation, we welcome you to contact our team.
01

What constitutes a civil conspiracy?

A civil conspiracy requires an agreement between two or more persons to act together for the purpose of causing harm to another, whether by lawful or unlawful means, resulting in actual damage to the plaintiff. Canadian law recognizes two varieties: predominant purpose conspiracy (where lawful conduct becomes tortious because of malicious intent) and unlawful means conspiracy (where the means themselves are unlawful and directed at the plaintiff). Both require proof of agreement, concerted action, and resulting damage.

02

How has the tort of civil conspiracy evolved over time?

Civil conspiracy has medieval origins as an action to redress abuse of the court's criminal process. It developed through the nineteenth century primarily as a tool to regulate organized labour and competitive business practices. The modern doctrine was shaped by Mogul Steamship, Crofter, and Lonrho in the UK, and by Canada Cement LaFarge and Pro-Sys Consultants in Canada, the latter finally distinguishing the two varieties cleanly.

03

What do you have to prove in a civil conspiracy claim?

For predominant purpose conspiracy: (1) agreement between two or more persons, (2) predominant purpose to injure the plaintiff, (3) damage results. For unlawful means conspiracy: (1) agreement, (2) conduct directed at the plaintiff, (3) unlawful means, (4) constructive intent to injure and resulting damage. Agreement is usually proven circumstantially through parallel conduct, common interests, coordinated timing, and communications.

04

How do you defend a civil conspiracy claim?

Common defences include: challenging the existence of any agreement (emphasizing independent decision-making), establishing legitimate business justification under the Crofter principle (predominant purpose conspiracy), demonstrating that unlawful means were not directed at the plaintiff or that harm was unforeseeable (unlawful means conspiracy), arguing lack of knowledge that the means were unlawful, and attacking causation and quantum of damages. Pleadings challenges under Rule 21 are often the first line of defence.

05

What remedies are available to victims of a civil conspiracy?

Successful plaintiffs may recover compensatory damages for economic loss caused by the conspiracy. Aggravated and punitive damages are more readily available in conspiracy cases than in many other torts, particularly where the conduct was deliberately targeted and egregious. Injunctive relief, including interim injunctions, Mareva orders, and Norwich orders, is often available to preserve assets or restrain ongoing conduct. Constructive trust and equitable tracing remedies may also apply where conspiracy funds can be followed.

Start your file

Civil conspiracy comes in two forms with different elements and different thresholds. Which one applies to your situation determines how the case is built.

Predominant purpose conspiracy requires proof that the defendants' primary aim was to harm the plaintiff, even if the means used were otherwise lawful. Unlawful means conspiracy sets a lower bar on intent but requires proof that the defendants used independently unlawful means. For plaintiffs, choosing the right form and marshalling evidence of agreement and intent is where the claim is won or lost before trial. For defendants, the distinction matters equally: the elements that must be proven against you differ, and so does the viable defence strategy.

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