UK Antitrust Law

Statutory Framework

UK competition law is principally governed by the Competition Act 1998 and the Enterprise Act 2002. The Competition Act reproduces the substance of EU Articles 101 and 102 TFEU through its Chapter I and Chapter II prohibitions. Chapter I prohibits agreements between undertakings, decisions by associations of undertakings, and concerted practices that may affect trade within the UK and have as their object or effect the prevention, restriction, or distortion of competition. Chapter II prohibits abuse of a dominant position that may affect trade within the UK. The Enterprise Act establishes the UK’s distinct merger control and market investigation regimes and created the Competition and Markets Authority (CMA), which became fully operational in April 2014.

The Competition Act 1998

The Chapter I prohibition (s. 2) closely mirrors Article 101 TFEU, including the four-part exemption test (efficiency gains, fair consumer share, indispensability, no elimination of competition). The Chapter II prohibition (s. 18) mirrors Article 102 TFEU, with the same non-exhaustive list of abuses: unfair purchase or selling prices, limiting production or markets, discriminatory conditions, and tying. UK courts and the CMA have consistently held that EU case law under Articles 101 and 102 remains highly persuasive post-Brexit. In Ping Europe Ltd v. CMA (2020), the Competition Appeal Tribunal (CAT) upheld a CMA fine of £1.45 million for resale price maintenance, applying the same analytical framework as under EU law.

CMA and Concurrent Regulation

The CMA is the primary competition authority with jurisdiction across all sectors. In regulated industries—communications, energy, water, rail, health, and financial services—sector regulators exercise concurrent competition powers. These include Ofcom, Ofgem, Ofwat, the ORR, the CMA’s Markets and Mergers directorates, the Payment Systems Regulator, and the FCA. The concurrency regime requires close coordination through the Concurrency Regulations and the CMA-Regulators Competition Network to ensure consistent application.

Merger Control

The Enterprise Act 2002 established a voluntary but suspensory merger control regime. Mergers meeting the “relevant merger situation” test (enterprises ceasing to be distinct and either the UK turnover threshold of £70 million or the share-of-supply test) may be referred to the CMA for a Phase II investigation if they raise a substantial lessening of competition (SLC) concern. The CMA has no power to block a merger without a court order but may accept binding undertakings in lieu of reference or impose remedies following a Phase II decision. The European Union (Withdrawal) Act 2018 ended the “one-stop shop” for EU mergers, giving the CMA jurisdiction over transactions that previously fell within the European Commission’s sole purview.

Market Investigations

The Enterprise Act also provides a market investigation tool unique among competition regimes. Where the CMA has reasonable grounds to suspect that features of a market (structure, conduct, or any combination) prevent, restrict, or distort competition, it may conduct a market study and, if concerns persist, launch a market investigation. Remedies may include structural measures (divestiture), behavioral measures, or recommendations to government. Notable investigations include the energy market investigation (2016), retail banking (2016), and online platforms and digital advertising (2020).

Appeals and Private Enforcement

Decisions of the CMA may be appealed to the CAT on the merits, not merely on judicial review grounds. The CAT can confirm, vary, set aside, or remit decisions and may impose, reduce, or increase penalties. Private enforcement has grown following the EU Damages Directive 2014/104, though continued divergence is expected. The CAT operates a follow-on action regime and also hears stand-alone claims. The Consumer Rights Act 2015 introduced opt-out collective proceedings for competition law infringements, enabling class actions before the CAT.

Post-Brexit Developments

UK competition law has developed independently since the end of the transition period on 31 December 2020. The CMA no longer coordinates with the European Competition Network (ECN), and parallel proceedings in respect of the same conduct before both the CMA and the European Commission are possible. The UK’s National Security and Investment Act 2021 introduced a mandatory notification regime for transactions in 17 sensitive sectors, operating alongside the competition merger control regime.