Antitrust authorities can check whether companies such as Meta Platforms comply with EU data protection rules during their investigations, Europe's top court said on Tuesday, a move likely to broaden regulators' scrutiny of Big Tech.

The case before the Luxembourg-based Court of Justice of the European Union (CJEU) concerns a 2019 German cartel office order to Meta to stop collecting users' data without their consent as such a practice constituted an abuse of its market power.

At issue is whether the German antitrust agency overstepped its authority by using its antitrust power to address data protection concerns, which are the remit of national data protection authorities.

Meta, owner of Facebook, Instagram and WhatsApp, challenged the finding, prompting a German court to seek advice from the CJEU.

"A national competition authority can find, in the context of the examination of an abuse of a dominant position, that the GDPR has been infringed," judges said, referring to EU privacy rules.

The CJEU however said antitrust regulators must "take into consideration any decision or investigation by the competent supervisory authority pursuant to that regulation."

"We are evaluating the Court's decision and will have more to say in due course," a Meta spokesperson said.

The case is C-252/21 Meta Platforms and others (User conditions for a social network).