Regulators in Brussels and the UK have launched formal competition investigations into Facebook, in a joint assault on the social media company’s use of customer data to dominate in core markets such as digital advertising. 

In a statement on Friday, the UK’s Competition and Markets Authority said it was investigating whether Facebook might be “abusing a dominant position in the social media or digital advertising markets through its collection and use of advertising data”.

Separately, Brussels said it was opening a formal antitrust investigation to assess whether Facebook violated EU law “by using advertising data gathered in particular from advertisers in order to compete with them in markets where Facebook is active such as classified ads”.