In a new challenge to Facebook's business model, the EU and the UK opened formal antitrust investigations yesterday to see if the world's largest social network is utilizing customers' data to unfairly compete with advertising.

Separately, the European Commission and the Competition and Markets Authority (CMA) in the United Kingdom announced that they will look into whether Facebook is misusing the large amount of data it collects from the over seven million businesses that advertise on Facebook Marketplace.

The launch of European Competition Commissioner Margrethe Vestager's first antitrust investigation against the world's largest social network is her latest battle with a US digital behemoth.