Britain's competition regulator said on Monday it had received a complaint about Google related to its market study this year on online platforms and digital advertising.
The complaint from a coalition of technology and publishing called Marketers for an Open Web (MOW) said they wanted the Competition and Markets Authority (CMA) to delay the launch of Google's so-called Privacy Sandbox technology.
MOW said this would remove features such as login and advertising from the open web and put them under Google control.
"We take the matters raised in the complaint very seriously, and will assess them carefully with a view to deciding whether to open a formal investigation under the Competition Act," the CMA said in a statement.
"If the urgency of the concerns requires us to intervene swiftly, we will also assess whether to impose interim measures to order the suspension of any suspected anti-competitive conduct pending the outcome of a full investigation."
Google did not immediately respond to a request for comment.
MOW said Google's Chrome browser and Chromium developer tools were being modified to give it greater control over how publishers, advertisers and other digital businesses can operate.
These changes are scheduled for full implementation in early 2021, MOW said in a statement.
"If Google releases this technology they will effectively own the means by which media companies, advertisers and technology businesses reach their consumers and that change will be irreversible," MOW director James Rosewell said.