The UK competition watchdog has accused Google of anti-competitive behaviour in the market for buying and selling ads on websites, in a move that follows similar investigations in the US and the EU. The Competition and Markets Authority (CMA) said it had found that Google has “abused its dominant position” in online advertising to the detriment of thousands of UK publishers and advertisers. The CMA said the vast majority of publishers and advertisers used Google’s ad tech services to bid for and sell advertising space, but the search company prevented rivals from offering competitive alternatives. The regulator has focused on Google’s role in three areas: its ownership of two tools for buying advertising space; its operation of an ad platform for publishers that allows them to manage their advertising space online; and its control of an ad exchange, AdX, that brings together advertisers and publishers, akin to matching buyers and sellers in a stock exchange. “The CMA is concerned that Google is actively using its dominance in this sector to preference its own services,” said the watchdog. “Google disadvantages competitors and prevents them competing on a level playing field to provide publishers and advertisers with a better, more competitive service that supports growth in their business.” In provisional findings published on Friday, the CMA found that since 2015 Google had abused its dominant position in the market through use of its buying tools and its inventory tool for publishers in order to strengthen the position of its ad exchange and to shield it from competition. It has also prevented rival ad inventory tools – known as publisher ad servers – from competing effectively with its own product, DoubleClick for Publishers, the CMA alleges. The CMA will consider any response from Google before reaching its final decision. The regulator can impose a fine of up to 10% of a company’s global turnover, with the amount depending on the seriousness of the infringement. It can also issue legally binding directions to bring the infringement to an end. In statement, Google said the CMA’s case was “flawed”. “Our advertising technology tools help websites and apps fund their content, and enable businesses of all sizes to effectively reach new customers,” said Dan Taylor, the Google vice-president of global ads. “The core of this case rests on flawed interpretations of the ad tech sector. We disagree with the CMA’s view and we will respond accordingly.” The US Department of Justice and the European Commission are also investigating Google’s activities in ad tech. In June 2023, EU regulators said Google may have to sell part of its adtech business to address its concerns, while on Monday the DoJ will accuse Google in court of monopolising the adtech market. Last month, a federal judge ruled that Google illegally monopolised control over the internet search market, in a decision that could lead to a partial breakup of the business.