The company on Wednesday said that up to 87 million people, mostly in the US, may have had their data improperly shared by political targeting firm Cambridge Analytica.

"To this day, we still don't know what data Cambridge Analytica have", Sandberg said.

"This work has not progressed past the planning phase, and we have not received, shared, or analysed anyone's data", a Facebook spokesperson told CNBC, the United States media outlet that broke the story today.

Sandberg explained that Facebook controls data on users at all times, creating tools so that advertisers can reach consumers most likely to want their product or service.

Facebook CEO Mark Zuckerberg will testify at a hearing before U.S. Congress next week.

After the detection of the theft of data Facebook says it had sent notices asking GSR and Cambridge Analytica to delete all data which was surreptitiously collected.

What this boils down to is Facebook tampering with the inboxes of its users, without notifying them. It's also restricting access that apps can have to data about users' events, as well as information about groups such as member lists and content.

Also, some users who logged in to Facebook through Android devices discovered that Facebook had been collecting information about phone calls they made and text messages they sent.

The NHS illegally handed the data of more than 1.5m patients to Google's artificial intelligence company DeepMind, the Information Commissioner's Office found previous year, during testing on kidney injuries.

Sheryl Sandberg, the company's chief operating officer, emphasized in an interview with NBC that Facebook depends on your data. "We will also label them and advertisers will have to show who paid for them".

Facebook is working to strengthen its system ahead of this year's US midterm elections and other elections around the world.

This could cost Facebook £625 billion, which is double the £317b it is worth, law professor Maureen Mapp argued. Verification of those page operators "will make it much harder for people to run pages using fake accounts, or to grow virally and spread misinformation or divisive content that way", he said. "It is on us that we didn't go back and do a forensic audit [of Cambridge Analytica]".

Sandberg's remarks in Thursday's interviews echoed Zuckerberg's in a conference call with reporters on Wednesday.

Last month, Facebook tried to come out ahead of Cambridge Analytica whistleblower Christopher Wylie by saying it had suspended the accounts of Wylie, Cambridge Analytica and its parent company, as well as the creator of an app that supplied Cambridge Analytica. The requirement for issue ads is new. "This will help raise the bar for all political advertising online".

Apparently, Facebook has been trying to get their hands on anonymised health data with a view to de-anonymising it against the personal data they hold.

Since a year ago, companies like Google and Twitter have also announced new political-ad-transparency rules. But a further probe by Facebook revealed that they had lied and were still in possession of the "loot".