SAN FRANCISCO • Facebook chief Mark Zuckerberg has vowed to "step up" to fix problems at the social media giant, as it fights a snowballing scandal over the hijacking of personal data from millions of its users.

"We have a responsibility to protect your data, and if we can't then we don't deserve to serve you," Mr Zuckerberg said in his first public comments on the harvesting of Facebook user data by a British firm linked to United States President Donald Trump's 2016 campaign.

Mr Zuckerberg announced new steps to rein in the leakage of data to outside developers and third-party apps, while giving users more control over their information through a special toolbar.

"This was a major breach of trust and I'm really sorry that this happened," he said in a televised interview with CNN. "Our responsibility now is to make sure this doesn't happen again."

Mr Zuckerberg said he will testify before Congress if he is the person at Facebook best placed to answer its questions, and that he is not opposed to regulating Internet titans such as the social network.

"I am actually not sure we shouldn't be regulated," the Facebook co-founder and chief executive told CNN.

"Technology is an increasingly important trend in the world; the question is more the right regulation than should it be regulated."

Mr Zuckerberg said measures had been in place since 2014 to prevent the sort of abuse revealed over the weekend but the social network needed to "step up" to do more.

The scandal erupted when a whistle-blower revealed that British data consultant Cambridge Analytica (CA) had created psychological profiles on 50 million Facebook users via a personality prediction app, created by a researcher named Aleksandr Kogan.

The app was downloaded by 270,000 people, but also scooped up their friends' data without consent - as was possible under Facebook's rules at the time.

Facebook said it discovered last week that CA may not have deleted the data as it certified.

"We should not have trusted Cambridge Analytica's certification, and we are not going to make that mistake again," Mr Zuckerberg said.

Facebook is reviewing how much data was accessed by every app at the social network, and will conduct full forensic audits if it notices anything suspicious, according to its chief executive.

"This was a breach of trust between Kogan, Cambridge Analytica and Facebook," Mr Zuckerberg wrote in a post on the social network's platform. "But it was also a breach of trust between Facebook and the people who share their data with us and expect us to protect it. We need to fix that."

His apology followed another day of damaging accusations against the world's biggest social network as calls mounted for investigations on both sides of the Atlantic.

US lawmakers want Mr Zuckerberg to testify.

"This isn't going to cut it," Representative David Cicilline, a Democrat from Rhode Island, said on Facebook in response to Mr Zuckerberg's remarks. "Mark Zuckerberg needs to testify before Congress."

That sentiment was echoed by Senator Richard Blumenthal, a Democrat from Connecticut.

"Mea culpas are no substitute for questions and answers under oath," said Mr Blumenthal, a member of the Judiciary Committee. "Congress has failed to hold Facebook accountable, and legislate protections on privacy, which are manifestly necessary."

Big Internet companies and small software developers alike are likely to face greater scrutiny over how they share customer information.

Facebook and Google and third-party services sit at the core of the contemporary Internet, enabling people to quickly share articles to Facebook from news websites and log into shopping apps using their Google accounts.

But the Facebook case has turned the application programming interfaces, or APIs, that enable such data sharing, into a new front in the growing battle between lawmakers and tech companies over the monitoring and securing of their vast platforms.

"All companies are going to need to do a lot more than just laissez-faire policy to manage third-party data access moving forward," said Mr Jason Costa, who helped run APIs at Pinterest, Twitter and Google, and now works at GGV Capital. "The days of (the) 'we're just a platform and can't be held responsible for how users use it' line that many companies use, is no longer going to be tenable."

AGENCE FRANCE-PRESSE, REUTERS, BLOOMBERG

SEE OPINION