Mark Zuckerberg has said it was a mistake to rely on Cambridge Analytica (CA) to delete tens of millions of Facebook users' data as he apologised for the "major breach of trust".
The site's founder said the political consultancy had provided formal assurances that information harvested from 50 million profiles had been destroyed after Facebook first learned of the breach in 2015.
Mr Zuckerberg said he was now open to Facebook being regulated and accepted that malign actors were trying to use the site for political ends.
The billionaire told CNN he would be happy to appear before US Congress "if it's the right thing to do".
"This was a major breach of trust, and I'm really sorry that this happened," he told CNN.
On Wednesday Mr Zuckerberg made his first public statement since the controversy erupted - via a Facebook post.
"I don't know about you, but I'm used to when people legally certify that they are going to do something, that they do it. But I think this was clearly a mistake in retrospect," Mr Zuckerberg told CNN.
Mr Zuckerberg said Facebook has already taken the most important steps to prevent such a situation from happening again.
He told the broadcaster the site would be reviewing thousands of apps in an "intensive process".
He said he was confident Facebook could "get in front" of the problem.
"This isn't rocket science. There's a lot of hard work we have to do to make it harder for nation states like Russia to do election interference," he said.