Britain has become one of the most important fronts in the legal challenge to Google’s advertising business. A series of collective proceedings in the Competition Appeal Tribunal now reaches across much of the company’s advertising ecosystem, from the publishers that sell digital inventory to the businesses that buy it and, in one case, the consumers who may ultimately bear part of the cost. The litigation falls into two broad groups. One concerns open display advertising and the technology that connects advertisers with publishers. The other concerns Google Search and the advertising sold alongside search results. Together, the cases offer an unusually broad examination of how Google’s position in search and advertising technology may have affected prices, revenues, competition and the distribution of value across the market.
The financial scale of the litigation is striking. The principal publisher action has been valued by its class representative at up to £13.6 billion. A newer display advertiser case seeks roughly £1.8 billion to £3.2 billion. The leading search advertiser action was initially estimated at around £5 billion, while a competing claim brought by Roger Kaye KC placed losses as high as £25.2 billion before that proceeding was stayed. A separate consumer action was initially valued at £7.3 billion. Each figure belongs to a distinct claim, but the amounts give some sense of the stakes now surrounding Google’s advertising business in Britain.
The display advertising cases
The most advanced proceeding is Ad Tech Collective Action LLP v Alphabet Inc. and Others. It began with separate claims brought by Claudio Pollack in 2022 and Charles Arthur in 2023, which the Tribunal later consolidated. The action was certified in 2024, Google’s efforts to challenge certification were unsuccessful, and the case is now well into disclosure ahead of a twelve-week trial scheduled to begin in September 2028. The class consists principally of UK publishers that sold display advertising on websites and apps, and the current claim period runs from October 2015 through November 2022. The class representative contends that Google’s conduct in the advertising technology market reduced the revenues publishers earned from the sale of their inventory.
The case centers on Google’s position across several layers of the display advertising system. Publishers use ad servers to manage advertising space. Advertisers use buying platforms to bid for that space. Exchanges connect the two sides through automated auctions. Google has operated important products at each level, including its publisher ad server, the AdX exchange, Google Ads and DV360. The publishers contend that Google used those positions to favor AdX and disadvantage competing exchanges, both through the treatment of rival platforms by its publisher technology and through the way its advertiser tools directed demand. Their economic theory is that weaker competition among intermediaries reduced the prices publishers received for their advertising inventory.
The case has become increasingly intertwined with enforcement elsewhere. The UK Competition and Markets Authority has been investigating Google’s display AdTech practices since 2022 and issued a statement of objections in 2024. The European Commission went further in 2025, imposing a €2.95 billion fine after finding that Google had abused dominant positions in AdTech by favoring its own services. The British private litigation is also drawing on a large evidentiary record developed outside the UK. Material from the U.S. Department of Justice proceedings, the Texas Attorney General’s investigation and the European Commission process is now entering disclosure in the publisher case. Years of regulatory and litigation work concerning the same products and practices are therefore converging in the UK proceeding.
A newer case, filed in May 2026, examines much of the same machinery from the advertiser side. AGC Collective Actions Limited v Alphabet Inc. and Others seeks damages for UK businesses that purchased Google display advertising on the open web. The proposed class is estimated at between 205,000 and 250,000 advertisers, with damages provisionally estimated at £1.827 billion to £3.173 billion. The case has not yet been certified, and its certification hearing is scheduled for December 2026. AGC alleges that Google Ads and DV360 favored AdX by inflating bids routed through Google’s exchange, imposing higher fees on bids submitted through rivals, or reducing those rival bids. It also challenges conduct involving Google’s publisher ad server and AdX, including practices such as Last Look, unified pricing rules and restrictions affecting competing exchanges.
AGC is important because it approaches the same display advertising system from the opposite side of the transaction. Publishers say Google’s conduct reduced what they received for advertising inventory. Advertisers say related conduct increased what they paid or diminished the value of what they bought. AGC alleges that businesses received less relevant or less useful inventory, paid higher prices for advertising that was displayed, or suffered both effects. The two proceedings involve many of the same products, practices and market relationships, and AGC has already contemplated case management alongside the publisher action. If the cases proceed in parallel, the Tribunal will be examining Google’s display advertising system from both the seller and buyer sides of the market.
Search advertising and the £25 billion claim
The search advertising cases concern a different part of Google’s business. They focus on Google’s position in general search and on the effect that alleged restrictions on search competition had on businesses buying advertisements alongside search results. The principal advertiser proceeding is now Or Brook Class Representative Limited v Google Inc. and Others, which the Tribunal certified in August 2026. Brook challenges arrangements involving Android devices, payments for default search placement and conduct involving Search Ads 360. The case places particular emphasis on Google’s agreements with Apple and on allegations that Google introduced functionality for its own search advertising services while withholding or delaying comparable functionality for Microsoft, making it harder for advertisers to manage campaigns across competing search platforms.
Brook’s theory is that these practices helped preserve Google’s scale and weakened competition in both search and search advertising. According to the claim, that allowed Google to charge higher prices for search advertising and reduced advertisers’ return on spend. The claimant’s economist initially estimated damages at around £5 billion, although the Tribunal has said limitation issues are likely to reduce that figure appreciably. The important procedural development is that Brook has now been certified and will proceed as the principal collective action on behalf of search advertisers.
The much larger £25.2 billion figure came from a competing search advertiser case filed by Roger Kaye KC in 2025. Kaye proposed to represent between 500,000 and 1.5 million UK advertisers and estimated aggregate losses at between £15.2 billion and £25.2 billion through the end of 2024. His case overlapped with Brook on Android and Google’s agreements with Apple, but it went further by alleging that Google had directly imposed excessive and unfair prices for search advertising. That additional excessive pricing theory helps explain why Kaye’s damages estimate was so much larger.
Brook and Kaye were initially competing to represent overlapping groups of advertisers, creating a carriage dispute before the Tribunal. The two claimant teams eventually reached an agreement under which Brook’s existing claim would continue, Kaye’s proceeding would be stayed, members of Kaye’s legal and expert teams would join the Brook structure, and Kaye would chair Brook’s consultative panel. The £25.2 billion figure therefore came from a real UK claim, but the broader Kaye pleading did not become part of Brook when the teams combined. The Brook case certified in August 2026 remains the operative search advertiser action.
The consumer case
The search litigation also extends downstream to consumers. Nikki Stopford v Alphabet Inc. and Others was certified in 2024 and concerns much of the same underlying conduct later pleaded by Brook, including Google’s Android arrangements and its agreements with Apple for default search status. Stopford contends that reduced competition allowed Google to charge businesses more for search advertising and that businesses then passed some portion of those costs into the prices consumers paid for goods and services. The original claim valued that alleged consumer loss at roughly £7.3 billion.
That creates a direct connection between the advertiser and consumer proceedings. Brook seeks recovery for businesses that allegedly paid inflated search advertising prices, while Stopford seeks recovery for the portion of those costs said to have been passed on to consumers. The two cases therefore examine the same alleged overcharge at different points in the economic chain. The eventual damages analysis will have to determine how much of any proven overcharge remained with advertisers and how much, if any, reached consumers.
The broader picture in Britain is unusually comprehensive. On the display side, publishers say Google’s conduct depressed their revenues while advertisers say related conduct raised prices or reduced advertising value. On the search side, advertisers say Google’s control of search allowed it to charge more for advertising, while consumers say some of those costs ultimately flowed through to them. Regulators are examining many of the same markets and practices, and evidence developed in U.S. and European proceedings is increasingly feeding into the UK record. Each case will turn on its own evidence, but together they have made Britain one of the most consequential jurisdictions in the continuing legal examination of Google’s advertising business.
Disclaimer: DARC helps businesses evaluate and pursue Google Ads recovery claims. This article is attorney advertising and general information, and it is not legal advice. Eligibility and potential recovery depend on the specific facts of each business’s advertising history.