The UK’s Competition Appeal Tribunal has officially certified a £5 billion class action lawsuit brought against Google on behalf of online advertisers. The suit, led by Or Brook Class Representative Limited (Brook), accuses the tech giant of exploiting its dominant market power across mobile operating systems, app distribution, general search services, and search advertising to the detriment of UK businesses.
The certification comes after the resolution of a carriage dispute in November 2025, which saw a competing claim by Mr Roger Kaye KC stayed, leaving Brook as the sole representative entity driving the legal action forward. The allegations brought by Brook align closely with those in another high-profile case, Nikki Stopford v Alphabet Inc., highlighting growing scrutiny over Google’s commercial ecosystem.
During the proceedings, Google raised objections spanning four primary areas, including concerns over Brook’s litigation funding arrangements and high legal costs, proposed amendments to the claim form, the specific definition of the class, and whether the suit should proceed on an opt-in or opt-out basis.
In its ruling, the Tribunal decided that the overall weight of evidence supported certifying the lawsuit on an opt-out basis. This structural choice means affected UK advertisers are automatically included in the legal action and eligible for compensation unless they actively opt out. Addressing Google’s objections, the Tribunal noted that while it shared some reservations regarding the scale of Brook’s legal expenses, these cost concerns were not sufficient to block the suit from proceeding.
To handle remaining technical details, including exact class definitions, limitation periods, and continuing loss, the Tribunal directed Brook to submit a letter of formalisation within 14 days of the decision’s publication. With certification granted, this massive claim moves one step closer to holding Google accountable for alleged anti-competitive harms in the advertising market.
