Facebook founder Mark Zuckerberg has admitted that the social network “made mistakes” that led to millions of Facebook users having their data exploited by a political consultancy.
Cambridge Analytica is accused of improperly using the data on behalf of political clients.
In a statement, Mr Zuckerberg said a “breach of trust” had occurred.
In a later interview with CNN he said he was “really sorry”, and pledged to take action against “rogue apps”.
He added that he was “happy” to testify before Congress “if it’s the right thing to do”.
In his statement posted on Facebook, he promised to make it far harder for apps to “harvest” user information.
“We have a responsibility to protect your data, and if we can’t then we don’t deserve to serve you,” Mr Zuckerberg said.