Facebook is facing investigations by authorities in Ireland, the EU, UK and US
Facebook boss Mark Zuckerberg has said he is "open" to testifying before US Congress on the Cambridge Analytica scandal.
Mr Zuckerberg has spoken out for the first time since his company shed tens of billions of dollars of its value amid concerns over the alleged harvesting of user data by the UK political consultancy firm.
London-based firm Cambridge Analytica, which was employed by Donald Trump's campaign team, is accused of using the data to influence the US election.
Facebook is facing investigations by authorities in Ireland, the EU, UK and US over reported data breach.
Mr Zuckerberg told CNN: "The short answer is I'm happy to (testify) if it's the right thing to do."
He suggested executives might be better qualified to answer questions, however.
He said that it was "clearly a mistake" to trust Cambridge Analytica in 2015 when it said it would delete the data it had gained from Facebook, the world's largest social media network.
Apologising for the "breach of trust", Mr Zuckerberg said: "I'm really sorry this happened.
"We have a basic responsibility to protect people's data."
He also said, however, that he had not seen a "meaningful number of people" deleting their accounts on the social network since news of the scandal broke.
The scandal has strengthened calls for Facebook and other social media to be subject to regulation, and Mr Zuckerberg said he was not against this.
"I'm not sure that we shouldn't be regulated," he said.
"I think technology is an increasingly important trend in the world.
"I actually think the question is more: what's the right regulation, rather than, yes or no, should it be regulated."
Mr Zuckerberg was speaking just hours after he posted a statement online saying his company "made mistakes" over the alleged misuse of users' data.
He also said that Facebook was committed to stopping interference in the US midterm election in November and upcoming elections in India and Brazil.