"We have a responsibility to protect your information. If we can't we don't deserve it," he said.
The ads ran in prominent positions in six British nationals, including the best-selling Mail on Sunday, The Sunday Times and The Observer -- which helped break the story -- as well as the New York Times, Washington Post and the Wall Street Journal.
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.