Mark Zuckerberg has said it was "clearly a mistake" to trust Cambridge Analytica (CA) when Facebook asked the British data firm to delete tens of millions of users' data.
The Facebook founder said CA had provided formal assurances that data harvested from 50 million profiles had been destroyed after the breach was revealed in 2015.
"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.
The billionaire, who has been called on to give evidence to MPs in person over the scandal, said he would be happy to appear before US Congress "if it's the right thing to do".
World Wide Web inventor Sir Tim Berners-Lee has described the Cambridge Analytica (CA) scandal as a "serious moment for the web's future".
The British scientist said it was time for all internet users to "build a web that reflects our hopes & fulfils our dreams more than it magnifies our fears & deepens our divisions".
Sir Tim was writing on Twitter after Facebook founder Mark Zuckerberg apologised for a 2015 breach that led to 50 million users' data being obtained by CA.
"I can imagine Mark Zuckerberg is devastated that his creation has been abused and misused. (Some days I have the same feeling #justsaying)," Sir Tim said.
"I would say to him: You can fix it. It won't be easy but if companies work with governments, activists, academics and web users we can make sure platforms serve humanity."
Culture Secretary Matt Hancock said the measures announced by Facebook boss Mark Zuckerberg do not go far enough.
"I saw overnight that Mark Zuckerberg has apologised and said that they are going to make some changes, but frankly I don't think those changes go far enough," he told BBC Radio 4's Today.
"It shouldn't be for a company to decide what is the appropriate balance between privacy and innovation and use of data, those rules should be set by society as a whole and so set by Parliament.
"That's the approach that we are taking - the big tech companies need to abide by the law and we are strengthening the law."
Culture Secretary Matt Hancock has told MPs that the "Wild West free-for-all of the internet companies" has to come to an end in light of the Cambridge Analytica scandal.
Mr Hancock, who made the comments during culture questions, went on to say that the incident represented a "turning point" in the debate.
He said: "We have shown and made the case over the last year that this Wild West free-for-all of the internet companies has got to come to an end. I think this is a turning point."