The investigation relates to the so-called “Jedi Blue” agreement struck in September 2018 for the participation of Meta’s Audience Network in Google’s Open Bidding programme, which is separately under investigation by the UK’s Competition Market Authority (CMA).

Google’s Open Bidding programme forms part of its ad tech services that intermediate between advertisers and publishers by real-time auctioning of online display advertising space on web sites or mobile apps.

Meta provides online display advertising services and, through its Meta Audience Network, participates in auctions for third-party publishers’ advertising space using Google’s and rivals’ advertising technology services.

If proven, the practices under investigation may breach EU competition rules on anticompetitive agreements between companies under Article 101 of the Treaty on the Functioning of the European Union (TFEU) and/or the abuse of a dominant position under Article 102 TFEU.

Margrethe Vestager, the European Commission’s executive vice-president in charge of competition policy, said: “Many publishers rely on online display advertising to fund online content for consumers.

“Via the so-called ‘Jedi Blue’ agreement between Google and Meta, a competing technology to Google’s Open Bidding may have been targeted with the aim to weaken it and exclude it from the market for displaying ads on publisher websites and apps.

“If confirmed by our investigation, this would restrict and distort competition in the already concentrated ad tech market, to the detriment of rival ad serving technologies, publishers and ultimately consumers.”

The Commission said it will now “carry out its in-depth investigation as a matter of priority”.