SAN FRANCISCO • Facebook's chief operating officer Sheryl Sandberg said that if she could relive this week over again - a week in which the social network has become engulfed in controversy over improper sharing of personal data of 50 million users - she and CEO Mark Zuckerberg would have spoken up a lot sooner.

"We definitely didn't realise the gravity of this issue sooner," Ms Sandberg said in a televised interview on CNBC on Thursday.

"We know this is an issue of trust, we know this is a critical moment for our company and the service we provide."

She said Facebook is open to regulation and other measures that could help re-establish trust with users.

"We are not going to say that we're not going to have issues," Ms Sandberg said. "We know that there are always going to be bad actors on our platform."

Facebook's board followed up with its own response.

"Mark and Sheryl know how serious this situation is and are working with the rest of Facebook leadership to build stronger user protections," said Ms Sue Desmond-Hellmann, the lead director of Facebook's board, in a statement.

"They have built the company and our business and are instrumental to its future."

BLOOMBERG