A group of US politicians added to growing scrutiny of Google’s proposed acquisition of Fitbit, urging the Department of Justice (DoJ) to carefully investigate potential impacts on competition and take action to stop the deal if necessary.

The politicians told attorney general William Barr they have concerns the transaction could reduce competition in several areas, including the wearables and nascent health technology markets, along with advertising and online search spaces already dominated by Google.

They dismissed a pledge by Google not to use Fitbit health data for targeted advertising, arguing the DoJ should be “extremely sceptical of unenforceable promises” given Google’s “revenue model is driven by the company’s ability to monetise user data”.

The group pressed the DoJ to “take any enforcement action that may be warranted” to prevent competitive harms, “including federal litigation to block the merger, if appropriate”.

At the beginning of the month, a group of consumer interest groups from across the globe called for close examination of the deal. The European Commission is also looking into it, with Financial Times reporting earlier this week the body had pressed Google for assurances around its use of Fitbit health data covering third-party access and a commitment not to use the information to boost its position in the search sector.