Google is facing a new class-action lawsuit in the UK, filed on behalf of advertisers who claim the company abused its dominant position in the market for online display advertising. The claim, lodged with the Competition Appeal Tribunal by AGC Collective Actions Limited and represented by law firm KP Law, seeks damages of up to £3 billion. It alleges that Google systematically favoured its own display advertising services while excluding competitors, forcing advertisers to pay more for less effective adverts.
The Allegations in Detail
The lawsuit centres on so-called display advertising – the banner-style promotions that appear when consumers browse websites, watch videos or use mobile apps, as distinct from the text-based adverts that appear alongside search engine results. According to the claim, Google leveraged its control over the ad tech supply chain to steer business towards its own products, harming rival ad exchanges, publisher ad servers and other intermediaries. The result, it is alleged, was higher costs and poorer performance for UK advertisers who bought display ads either directly from Google or through a media agency.
The claim asserts that Google holds a dominant position in the UK’s online display advertising market, a sector estimated to be worth £16.7 billion in 2024. Estimates cited in the research briefing suggest Google controls between 50% and 90% of the intermediary markets that connect advertisers with publishers. The company’s ad tech tools are described as ubiquitous, giving it a powerful gatekeeping role in the digital ad ecosystem.
These allegations mirror findings by regulators around the world. In September 2024, the UK’s Competition and Markets Authority (CMA) issued a statement of objections provisionally concluding that Google had harmed competition by using its dominance in display advertising to favour its own ad tech services. In the European Union, the European Commission fined Google €2.95 billion (£2.55 billion) in September 2025 for breaching antitrust rules, finding that the company abused its dominant position to distort competition in the ad tech industry. Google has appealed that fine, calling it “wrong”.
In the United States, a federal judge ruled in April 2025 that Google had illegally monopolised the publisher ad server and ad exchange markets for open-web display advertising, following a civil antitrust suit filed by the US Department of Justice in January 2023. The judge’s decision underscored the same pattern of self-preferencing alleged in the UK claim.
A Broader Pattern of Legal Action
The new display advertising lawsuit is far from an isolated challenge. Google is already defending a separate UK claim, led by Roger Kaye KC, which accuses the company of monopolising the search advertising market. That case alleges that Google’s agreements with mobile phone manufacturers to make Google Search the default search engine inflated prices for advertisers, seeking up to £25 billion in compensation. Another search advertising claim, brought by Or Brook Class Representative Limited, seeks up to £5 billion on similar grounds. KP Law is also involved in a £15 billion claim on behalf of advertisers who paid for Google Search ads between 2011 and 2025.
The CMA has been a particularly active regulator. It launched a formal investigation into Google’s ad tech conduct in May 2022, and in October 2025 designated Google as having “strategic market status” for its general search and search advertising services – a move that gives the watchdog new powers to oversee the company’s behaviour. In Europe, the Commission’s recent €2.95 billion fine followed years of scrutiny, and the Commission has indicated that only structural separation, such as a forced divestiture of Google’s ad tech business, may fully address the inherent conflicts of interest. Google has proposed changes to its products in an effort to avoid such a break-up.
Other legal cases are also in play. In June 2024, the UK Competition Appeal Tribunal certified a £13.6 billion ad tech claim brought by Ad Tech Collective Action LLP, which is being handled by Hausfeld & Co. LLP and Humphries Kerstetter LLP. The video-sharing platform Rumble has sued Google for allegedly monopolising the ad tech stack. And in France, Google was fined €220 million in June 2021 by the competition authority for ad tech market abuses.
Google’s Response
Google has consistently denied engaging in anti-competitive behaviour. The company maintains that its services are chosen by consumers and advertisers because they are helpful and effective, not because of a lack of alternatives. It has argued that the digital advertising market is dynamic and competitive, with many rivals offering different tools and platforms. The company is appealing the European Commission’s €2.95 billion fine.
A spokesperson for KP Law and the proposed class representative for the UK claim said: “Google has a well-documented track record of anti-competitive behaviour in the online digital advertising space, in particular in relation to ad tech, as recognised by courts and regulators across the US and Europe.”
