Facebook says the personal information of up to 87 million users may have been improperly shared by the US social media company with a British political consulting firm, up from a previous estimate of more than 50 million.

Axar.az reports citing AP.

Facebook CEO Mark Zuckerberg said in a conference call with reporters on Wednesday that he accepted blame for the data leak, while also saying he was still the right person to head the company he founded.

The data leak, which has mostly affected Facebook members in the US, has angered users, advertisers and lawmakers.

Zuckerberg will testify about the matter next Tuesday and Wednesday during two US congressional hearings.

“When you’re building something like Facebook that is unprecedented in the world, there are going to be things that you mess up,” Zuckerberg said, adding that the important thing was to learn from mistakes.

He said the social networking service had not seen “any meaningful impact” on usage or advertisement sales since the scandal.

Facebook, the world's largest social media company with more than 2 billion monthly active users, made almost all its $40 billion in revenue last year from advertising.

One reason Facebook and other internet companies collect personal information from users is to deliver targeted advertising.

Facebook first acknowledged last month that the personal information of about 50 million of users wrongly ended up in the hands of London-based Cambridge Analytica.

Zuckerberg, on the call with reporters, said Facebook should have done more to audit and oversee third-party app developers like the one that Cambridge Analytica hired in 2014. He said the company was taking steps to restrict which personal data is available to third-party app developers.

Most of the up to 87 million people whose data was shared with Cambridge Analytica were in the United States, Facebook Chief Technology Officer Mike Schroepfer wrote in a blog post.

The previous estimate of more than 50 million Facebook users affected by the data leak came from a US and UK newspaper, The New York Times and The Observer.

Facebook stocks have dropped more than 16 percent since the Cambridge Analytica scandal broke.

Zuckerberg said Facebook came to the higher estimate by looking at the number of people who had downloaded a personality test application created by Cambridge University academic Aleksandr Kogan, or about 270,000 people, and then adding in the number of friends they had.

The data leak scandal has prompted investigations by the US Federal Trade Commission, Britain’s Information Commissioner’s Office and by some 37 US states.