Zuckerberg repeated that Facebook had changed the rules so no such data breach could happen again. Facebook chief Mark Zuckerberg took out full-page ads in almost all of Britain's national newspapers Sunday to apologise for a huge data privacy scandal.
"We have a responsibility to protect your information. If we can't we don't deserve it," the back page ads state.
Zuckerberg explained there was a quiz developed by a university researcher "that leaked Facebook data of millions of people in 2014".
"This was a breach of trust, and I'm sorry we didn't do more at the time. We're now taking steps to make sure this doesn't happen again," he said.
The statement reflects public statements Zuckerberg made last week after the row prompted investigations in Europe and the United States, and sent Facebook's share price plunging.
Zuckerberg repeated that Facebook had changed the rules so no such data breach could happen again.
"We're also investigating every single app that had access to large amounts of data before we fixed this. We expect there are others," he wrote.
"And when we find them, we will ban them and tell everyone affected."
There was no mention of the British firm accused of using the data, Cambridge Analytica, which worked on US President Donald Trump's 2016 campaign.
It too has blamed the University of Cambridge researcher, Alexsandr Kogan, for any potential breach of data rules.
Kogan created a lifestyle quiz app for Facebook which was downloaded by 270,000 people, but allowed access to tens of millions of their contacts.
Facebook says he passed this to Cambridge Analytica without its knowledge. Kogan says he is being made a scapegoat.
Explore further: Facebook's Zuckerberg admits mistakes—but no apology (Update)