Prime Minister Theresa May and EU justice commissioner Vera Jourova have added their voices to concerns raised over Facebook’s treatment of personal data as shares in the social media giant plummeted.

Facebook and Cambridge Analytica have been accused of misleading MPs after reports claimed the US data firm harvested data from more than 50 million social media profiles without consent.

A spokesman for the Prime Minister backed the decision of Information Commissioner Elizabeth Denham to investigate Cambridge Analytica over an alleged data breach, which you can read all about here.

“The allegations are clearly very concerning,” a spokesman said. “It is essential that people can have confidence that their personal data will be protected and used in an appropriate way.

“So it is absolutely right that the Information Commissioner is investigating this matter. We expect Facebook, Cambridge Analytica and all the organisations involved to cooperate fully.”

Jourova said she plans to discuss the matter with Facebook and the US government on a planned visit to the United States this week.

“From a European Union perspective, the misuse for political purposes of personal data belonging to Facebook users – if confirmed – is not acceptable,” the European Commission said in a statement.

Antonio Tajani, the head of the European Parliament, urged Facebook to take more responsibility.

He wrote on Twitter: “Allegations of misuse of Facebook user data is an unacceptable violation of our citizens’ privacy rights.”

Facebook shares fell four per cent in pre-market trading on Monday, Reuters reported. Compared with the market’s close on Friday, that would knock $21.5 billion (£15.3bn) off its value of $538bn.

We ran a series of articles on Facebook’s use of data last year, from how it targets you with tagging and location to accessing your phone and emails, whether people know you’ve viewed their profile and making friend suggestions from Tinder and other apps.