If you have ever paid to put a banner advertisement on a website, a video platform or a mobile app, there is a chance you paid more than you should have. That, at least, is the argument that a growing number of legal actions in the UK are making against Google.
The latest was filed this week by AGC Collective Actions Limited, represented by law firm KP Law, with the UK's Competition Appeal Tribunal. The claim seeks damages of up to £3 billion and alleges that Google abused its dominant position in the online display advertising market by favouring its own services while shutting out competitors. The result, the claim argues, was that advertisers paid inflated prices for advertising that was less effective than it should have been.
Display advertising is the category of online promotion that appears as banner graphics, video placements and promotional panels while users browse websites, watch streaming content or use mobile apps. It is distinct from search advertising, which appears when users look something up in Google's search engine. The two markets operate differently and are regulated separately, though Google holds dominant positions in both.
A spokesperson for KP Law described the scale of Google's alleged conduct as well documented: "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. It is only right that UK advertisers have their day in court and that Google now answers for its entrenched and longstanding anti-competitive behaviour. We look forward to working on behalf of advertisers to secure compensation for them from Google."
Google has not yet responded publicly to this specific filing. In the parallel publisher claim, Google described the allegations as speculative.
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The other case already in progress
The new £3 billion claim is separate from a larger action already proceeding through the Competition Appeal Tribunal. That case, brought by Ad Tech Collective Action LLP on behalf of UK publishers rather than advertisers, seeks £13.6 billion in damages and alleges that Google abused its dominant position in a way that caused significant financial losses to websites and apps that rely on display advertising revenue.
The publisher claim received a collective proceedings order from the tribunal in March 2025, clearing it to proceed as a formal collective action. It is expected to go to trial in 2026. Publishers covered by that claim include those who received display advertising revenue through Google's systems between January 2014 and November 2022, and are automatically included unless they opted out before the deadline in May 2025.
The two claims represent different sides of the same market. Publishers are the websites and apps that carry advertising. Advertisers are the businesses that buy it. Both groups are arguing they were harmed by Google's control of the technology infrastructure connecting the two.
The broader regulatory picture
The UK legal actions do not exist in isolation. France's competition authority fined Google €220 million over similar conduct. The European Commission has pursued its own investigation. In the United States, the Department of Justice took Google to court over its advertising technology practices, and a federal judge in Virginia found in April 2025 that Google had illegally monopolised the online advertising technology market.
Google appealed the US ruling. It also filed an appeal against the EU's related findings. The company's consistent position across all of these proceedings is that the allegations misrepresent how the advertising market functions and that its practices benefit publishers, advertisers and users.
What neither Google nor anyone else disputes is the underlying market structure. Google owns the dominant publisher ad server, which controls how publishers manage and sell their advertising inventory. It owns the dominant advertiser platform, through which most large advertisers buy display ads. And it operates the dominant advertising exchange, which sits in between the two and facilitates transactions. Owning all three positions in a single market is what regulators in multiple jurisdictions are examining.
The UK advertiser claim is at an earlier stage than the publisher action. The Competition Appeal Tribunal must now decide whether to grant a collective proceedings order, which would allow it to proceed as a class action covering all affected UK advertisers. If granted, the path to trial is long, expensive and uncertain. Legal proceedings of this kind against large technology companies routinely last years.
What is no longer uncertain is the direction of travel. Google is being pursued for billions of pounds in the UK alone, by two different groups, for two different sides of the same alleged market abuse. The trials, if and when they conclude, will either confirm what regulators across three continents have been arguing or produce the most significant legal vindication of a major technology company since the last time this was tried.
Sources:
- LBC News — Google facing £3bn legal claim accusing it of monopolising display ads market
- Irish News — Google facing £3bn legal claim accusing it of monopolising display ads market
- Globe Newswire — Google Ad Tech Claim gets green light from UK Competition Appeal Tribunal
- Press Gazette — £13.6bn publisher adtech claim versus Google takes step forward
- UK Competition Appeal Tribunal
