Anti-competitive conduct under the Competition and Consumer Act 

The Competition and Consumer Act 2010 (Cth) has two great halves. One is the Australian Consumer Law, covered elsewhere in this module. The other is a set of competition law provisions aimed not at protecting individual consumers directly, but at protecting the competitive process itself — the general prohibition in s 45 asks whether conduct has the purpose or likely effect of substantially lessening competition², on the view that vigorous competition between firms is what ultimately benefits consumers through lower prices, better quality and more innovation. This article introduces the three core competition prohibitions — cartel conduct, misuse of market power, and anti-competitive mergers — and the basic distinction that runs through all of them.

The purpose of the competition provisions

The competition provisions exist to preserve the process of rivalry between firms in a market, not to protect any particular competitor from losing a fair fight. A firm that wins customers by being cheaper, better or more innovative is not acting unlawfully merely because rivals suffer as a result — that is competition working as intended. The law intervenes only where conduct threatens to damage the competitive process itself. Enforcement is led nationally by a dedicated competition regulator, the Australian Competition and Consumer Commission (ACCC), which investigates suspected contraventions and can bring proceedings, alongside more limited private rights of action available to those directly affected.

Cartel conduct

Cartel conduct covers arrangements between competitors that fix prices, restrict outputs, allocate markets or customers between themselves, or rig bids. This category is treated as close to a per se prohibition: because this kind of conduct between competitors is regarded as inherently harmful to competition, a claim does not generally require separate proof that the arrangement, in the particular case, actually or likely substantially lessened competition in a market. The character of the conduct itself — competitors agreeing to suppress rivalry between themselves rather than compete on the merits — is treated as sufficient, subject to limited statutory exceptions and processes by which competitors can seek clearance for conduct that might otherwise be caught. The most serious cartel conduct can also attract criminal liability, in addition to civil contravention.

Misuse of market power

Misuse of market power is different in structure. It targets a firm with substantial market power engaging in conduct that has the purpose, effect, or likely effect of substantially lessening competition in a market. Queensland Wire Industries Pty Ltd v Broken Hill Pty Co Ltd (1989) 167 CLR 177¹ is the leading illustration: a dominant steel manufacturer's refusal to supply a competitor was found to misuse its market power because an equivalent firm without that power could not have refused supply in the same way. Unlike cartel conduct, this is not a per se rule: a claim requires proof both that the firm holds substantial market power and that its conduct has, or is likely to have, the relevant anti-competitive purpose or effect. Simply possessing market power, or competing aggressively even from a position of strength, is not unlawful — the provision targets the misuse of that power to damage rivals' ability to compete on the merits, not success achieved by superior efficiency or attractiveness to customers.

Anti-competitive mergers

The third prohibition addresses acquisitions — mergers, share or asset purchases — that would have the effect, or be likely to have the effect, of substantially lessening competition in a market. Like misuse of market power, this is an effects-based inquiry rather than a per se rule: it requires identifying the relevant market and assessing, often on a forward-looking and largely economic basis, what would likely happen to competition in that market if the acquisition proceeded. For an acquisition put into effect on or after 1 January 2026 that is required to be notified, that test is applied through a notification process, described next.

As at 3 October 2026, merger review under the Act includes a mandatory notification regime for acquisitions that meet the thresholds or fall within the classes the Minister has determined. The Treasury Laws Amendment (Mergers and Acquisitions Reform) Act 2024 (Cth) inserted the new provisions, in Part IVA and Division 1A of Part IV, and the requirement to notify applies only to acquisitions put into effect on or after 1 January 2026. It does not apply to an acquisition for which the ACCC granted a merger authorisation, or advised a party in writing that it did not intend to take action under the Act about s 50, between 1 July 2025 and 31 December 2025, if the acquisition is put into effect within 12 months of that authorisation or advice (s 189(2)).⁵ Subject to the exceptions in Subdivisions B and C of Division 2, an acquisition is required to be notified to the ACCC if it is put into effect on or after that date, occurs in circumstances or falls within a class that the Minister has determined by legislative instrument, and is not excluded by a further determination (s 51ABO). Schedule 5 of the Treasury Laws Amendment (Strengthening Financial Systems and Other Measures) Act 2025 (Cth) replaced s 51ABO and s 189(1) with effect from 5 December 2025; s 189(1) now states only that Division 2 of Part IVA does not apply to an acquisition to which s 189(2) applies.⁶ The exceptions include internal restructures (s 51ABD), certain acquisitions of shares that do not result in control (s 51ABS, unless the Determination brings them back within a class that must be notified), certain acquisitions of shares in Chapter 6 entities that do not move anyone's voting power across the thresholds in s 51ABT(1) and acquisitions that the ACCC has determined, on a waiver application, need not be notified (s 51ABV). The circumstances must be set wholly or partly by reference to a specified threshold, which may relate to the value of the acquisition, the turnover of a person or business, the level of concentration in a market or a person's assets (s 51ABP(2)–(3)).³ The Act does not state the figures, so the current thresholds are a matter for those instruments and for the ACCC. The Competition and Consumer (Notification of Acquisitions) Determination 2025 (Cth) also determines classes of acquisition that must be notified, including acquisitions by Coles and Woolworths and their connected entities of supermarket businesses and of certain land (ss 3-1, 3-2). A notification may also be made of an acquisition that is not required to be notified (s 51ABW(1)).

Notification is the route to clearance. The ACCC may determine that a notified acquisition may be put into effect or that it must not be, and may make the second determination only if the notification is subject to phase 2 review, it has given a notice of competition concerns, and it is satisfied that the acquisition would, or would be likely to, substantially lessen competition in any market (s 51ABZE(1)–(2)). Both s 50(3) and s 51ABZH(4) provide that an acquisition may substantially lessen competition if it would, in all the circumstances, have the effect, or be likely to have the effect, of creating, strengthening or entrenching a substantial degree of power in the market, but s 50 does not apply to a notified acquisition (s 50(5B)). The notifying party may apply to the Australian Competition Tribunal for review of the ACCC's determination, as may another person the Tribunal allows (s 100C(1), (3)).⁴

Failure to notify has direct consequences. An acquisition that is required to be notified but is not a notified acquisition is stayed (s 51ABE(2)), and any person who puts a stayed acquisition into effect contravenes s 45AY, a provision that also covers notified acquisitions that are stayed pending the ACCC's determination. A principal party to an acquisition that is required to be notified also contravenes s 45AW if it is put into effect when it is not a notified acquisition, has no notification with an effective notification date, or has a latest notification that is stale.³ Both are Part IV provisions, for which the Federal Court may order pecuniary penalties (s 76(1)). The Act also makes some acquisitions put into effect in breach of a stay void, and gives the Federal Court powers, on the ACCC's application, to declare an acquisition void or make other orders such as divestiture (ss 45AZA, 77D, 77E). How those provisions apply turns on the circumstances and on when the acquisition was put into effect, so the sections themselves govern a given transaction.⁴

Per se versus effects-based prohibitions

The recurring distinction across these three prohibitions is worth stating explicitly. Per se-style prohibitions, most clearly cartel conduct, are assessed essentially by the category or character of the conduct itself, without a separate case-by-case inquiry into its actual competitive effect. Effects-based prohibitions, covering misuse of market power, anti-competitive mergers, and other arrangements outside the cartel categories, require proof that the conduct has, or is likely to have, the purpose or effect of substantially lessening competition in a properly defined market — a fact-intensive, economically grounded inquiry rather than a simple checklist.

Remedies and enforcement

At a conceptual level, contraventions can attract substantial pecuniary penalties, injunctions, divestiture-type orders in the merger context, disqualification orders against individuals, and compensation for parties who suffer loss. Enforcement is led by the national competition regulator, with the most serious cartel conduct also capable of attracting criminal consequences.

Applying this in a problem question

1. Classify the conduct: an agreement between competitors (possible cartel conduct), unilateral conduct by a powerful firm (possible misuse of market power), or a proposed acquisition (possible anti-competitive merger).
2. For cartel-type conduct, check whether it falls within the prohibited categories — price fixing, output restriction, market or customer allocation, or bid rigging.
3. For misuse of market power, establish substantial market power first, then assess the purpose or likely effect of the conduct on competition.
4. For a merger, first ask whether the acquisition is required to be notified to the ACCC (put into effect on or after 1 January 2026, within a determined threshold or class, and not excluded or waived) and, if so, whether it has been; then define the relevant market and assess the likely effect of the acquisition on competition in that market.
5. Keep vigorous, lawful competition analytically separate from conduct that damages the competitive process itself.
6. Identify the likely remedy and who is positioned to seek it — the regulator, or a party that has suffered loss.