Apple and Google could be forced to loosen their grip on mobile systems after the United Kingdom’s competition watchdog launched an in-depth market investigation Tuesday.

The U.K.’s Competition and Markets Authority’s (CMA) decision comes after an earlier survey concluded that Apple and Google “hold all the cards” in mobile ecosystems, allowing them to “exercise a stranglehold over operating systems, app stores and web browsers.”

The CMA’s findings state that 97 percent of all mobile web browsing in the U.K. in 2021 occurred on browsers powered by Apple’s Safari or Google’s Chrome. Respondents to the CMA’s study also highlighted how Apple restricts cloud gaming through its App Store.

“Many UK businesses and web developers tell us they feel that they are being held back by restrictions set by Apple and Google,” Sarah Cardell, interim chief executive of the CMA, said Tuesday. “We plan to investigate whether the concerns we have heard are justified and, if so, identify steps to improve competition.”

In a statement, Apple said that it would “continue to engage constructively with the Competition and Markets Authority to explain how our approach promotes competition and choice.” Google didn’t immediately respond to POLITICO’s request for comment.

The CMA is required to end a market investigation within 18 months. If it concludes there is anti-competitive behavior in the market, it can impose remedies on firms and make recommendations to the government on regulation.

U.K. Chancellor Jeremy Hunt announced last Thursday that the government would present regulations to combat Big Tech's anti-competitive abuses, in the form of a Digital Markets Competition & Consumers Bill, before May next year.

The CMA’s Cardell said Tuesday that the new rules would address the “sorts of issues” raised in Apple and Google’s dominance over mobile ecosystems. The CMA’s Digital Markets Unit could receive new regulatory powers as early as October next year.