The European Commission has opened a formal antitrust investigation into an advertising deal between Google and Meta, formerly Facebook.

The Commission wants to assess whether an agreement between the two companies for online display advertising services may have breached EU competition rules.

The investigation concerns a September 2018 agreement, which Google code-named "Jedi Blue", between Google and Meta for the participation of Meta's Audience Network in Google's "Open Bidding programme".

The Commission says it is concerned that the agreement may form part of efforts to exclude ad tech services competing with Google's Open Bidding programme.

"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," said European Commission Executive Vice-President Margrethe Vestager.

Ms Vestager is also in charge of competition policy.

Google provides advertising technology services that intermediate between advertisers and publishers by real time auctioning of online display advertising space on web sites or mobile apps, including through its Open Bidding programme.

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.

The UK's Competition Market Authority has launched its own investigation into the agreement between Google and Meta.

Google said today that the allegations made about the advertising agreement are false.

"This is a publicly documented, pro-competitive agreement that enables Facebook Audience Network (FAN) to participate in our Open Bidding program, along with dozens of other companies," a Google spokesperson said.

"FAN's involvement is not exclusive and they don't receive advantages that help them win auctions," the spokesperson added.

Meta said that its non-exclusive bidding agreement with Google and the similar agreements it has with other bidding platforms, have helped to increase competition for ad placements.

"These business relationships enable Meta to deliver more value to advertisers and publishers, resulting in better outcomes for all. We will cooperate with both inquiries." a Meta spokesperson said.