The U.K.’s antitrust watchdog launched an investigation into the Google Play app store over suspected anticompetitive conduct, alongside a sweeping study taking aim at Alphabet Inc. and Apple’s “strong grip” over mobile technologies.

Marking the latest broadside against Silicon Valley from an increasingly interventionist U.K. regulator, the Competition and Markets Authority will probe suspected breaches of competition law in Google’s rules over in-app payments in its mobile store in the U.K., it said Friday.

It set out various other possible interventions to tackle the apparent dominance of the two Big Tech giants in a flurry of statements on Friday.

It announced a deeper planned study into Apple and Google’s market power in mobile browsers and Apple’s in-cloud gaming.

“When it comes to how people use mobile phones, Apple and Google hold all the cards,” CMA Chief Executive Officer Andrea Coscelli said in a statement.

“As good as many of their services and products are, their strong grip on mobile ecosystems allows them to shut out competitors, holding back the British tech sector and limiting choice.”

He said Friday’s announcements add to eight cases currently open against major tech companies.

Google is currently the subject of at least two other British investigations mainly focused on its ad tech.

The watchdog published a 356-page market study into mobile ecosystems which took a year to compile, researching devices, operating systems and apps, after it previously voiced fears Google and Apple’s dominance could stifle competition.

“We respectfully disagree with a number of conclusions reached in the report, which discount our investments in innovation, privacy and user performance,” Apple said in a statement.

Android phones offer more choice than rival platforms and Google Play has launched businesses and helped create jobs, a Google spokesperson said.

“We regularly review how we can best support developers and have reacted quickly to CMA feedback in the past. We will review the report and continue to engage with the CMA.”

The CMA is waiting for the government to pass legislation which gives its new Digital Markets Unit the power to enforce more types of intervention.

The CMA found Apple and Google have “a gatekeeper role” in various parts of the mobile ecosystem and it suggested various remedies it could consider, including the following:

• Removing or changing restrictions on third-party app stores and third-party browsers.

• Making it easier for users to choose alternatives to Apple and Google, and to switch from Apple to Google operating systems.

• Addressing the sales commissions charged in app stores.

Although software giant Oracle Corp. said competition would benefit if Google’s Android mobile operating system was split out from its parent company, the report shows the CMA didn’t find a case to pursue structural breakups.

“Should Apple and Google act against consumers’ interests by making it unreasonably difficult for competing apps to successfully enter and expand, then separation could be reconsidered as an alternative,” the CMA reportsaid.