Google plans to end support for third-party cookies in the Chrome browser and its Chromium engine, a decision that has prompted an investigation by the U.K.’s Competition and Markets Authority (CMA).

According to the CMA, it will investigate whether the proposals “could cause advertising spend to become even more concentrated on Google’s ecosystem at the expense of its competitors.”

Third-party cookies help businesses target advertising effectively and fund free online content, such as news. Privacy advocates say they also allow companies to track consumers’ behavior across the web.

Google’s collection of changes, referred to as the Privacy Sandbox, would disable third-party cookies and replace them with new advertising targeting tools and what the company believes are better privacy protections.

The CMA said that its recent study into online platform digital advertising revealed that they could undermine competition and the ability of publishers to generate revenue. This would further solidify Google’s already dominant position in the market.

The CMA said it received complaints from Marketers for an Open Web Limited, a group of newspaper publishers and technology companies, which says Google is abusing its dominant position. The group urged the CMA to block the move.