He says "this was a breach of trust"
The CEO of Facebook, Mark Zuckerberg, has broken his silence over the Cambridge Analytica scandal.
The founder of the social media giant has said the platform has "made mistakes".
It is currently facing investigations by authorities in Ireland, the EU, UK and US over a reported data breach that impacted more than 50 million individuals.
UK-based data firm Cambridge Analytica, which was hired by Donald Trump's campaign team, is accused of using millions of Facebook profiles without authorisation to predict and influence the US election.
The board of Cambridge Analytica announced Tuesday it had suspended its CEO Alexander Nix pending a full independent investigation.
In a statement posted on Facebook, Mr Zuckerberg says: "We have a responsibility to protect your data, and if we can't then we don't deserve to serve you."
Posting a timeline of events, he says that in 2013, a Cambridge University researcher named Aleksandr Kogan created a personality quiz app, which was installed "by around 300,000 people who shared their data as well as some of their friends' data."
Mr Zuckerberg explains: "In 2014, to prevent abusive apps, we announced that we were changing the entire platform to dramatically limit the data apps could access.
"Most importantly, apps like Kogan's could no longer ask for data about a person's friends unless their friends had also authorized the app."
Then he says: "In 2015, we learned from journalists at The Guardian that Kogan had shared data from his app with Cambridge Analytica.
"It is against our policies for developers to share data without people's consent, so we immediately banned Kogan's app from our platform, and demanded that Kogan and Cambridge Analytica formally certify that they had deleted all improperly acquired data. They provided these certifications.
"Last week, we learned from The Guardian, The New York Times and Channel 4 that Cambridge Analytica may not have deleted the data as they had certified.
"We immediately banned them from using any of our services. Cambridge Analytica claims they have already deleted the data and has agreed to a forensic audit by a firm we hired to confirm this. We're also working with regulators as they investigate what happened."
"This was a breach of trust between Kogan, Cambridge Analytica and Facebook. 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."
"I started Facebook, and at the end of the day I'm responsible for what happens on our platform. I'm serious about doing what it takes to protect our community."
Facebook suspended Cambridge Analytica when reports emerged that the data company did not delete information about Facebook users that had been inappropriately shared.
In a previous statement, Facebook said: "The entire company is outraged we were deceived.
"We are committed to vigorously enforcing our policies to protect people's information and will take whatever steps are required to see that this happens."
It comes as the European Parliament invited Mr Zuckerberg to appear before it to answer questions.
President Antonio Tajani said he invited Mr Zuckerberg to "clarify before the representatives of 500 million Europeans that personal data is not being used to manipulate democracy."
The Oireachtas Communications Committee is also set to call Facebook and the Data Protection Commissioner to appear before it over the Cambridge Analytica scandal.
The Green Party said the committee has agreed to its request. It is expected the committee will consider the issue in mid-April.
While the chair of a UK culture committee, Damian Collins, said he has written to the Facebook chief executive to formally request he appear before them.