Facebook chief executive Mark Zuckerberg has said he "absolutely didn't intend to defend" Holocaust deniers following an interview where he said he would not ban their presence on the social network.
In an interview earlier this week, Mr Zuckerberg said he would not ban Holocaust deniers from Facebook because "there are things that different people get wrong".
However, he later sought to deflect the remarks. In an email to the editor of tech website Recode, Mr Zuckerberg said: "There's one thing I want to clear up. I personally find Holocaust denial deeply offensive, and I absolutely didn't intend to defend the intent of people who deny that."
Facebook has been facing calls to clean up the social network and block sources of conspiracy theories and fake news. The site's own community guidelines ban hate speech, but Mr Zuckerberg said that it was hard to ban speech like Holocaust denial as it was hard to "understand the intent".
Mr Zuckerberg's attempt suggest defending free speech should extend to Holocaust deniers on Facebook drew swift condemnation.
"Holocaust denial is a willful, deliberate and longstanding deception tactic by anti-Semites that is incontrovertibly hateful, hurtful, and threatening to Jews," said Jonathan Greenblatt, of US Jewish rights group the Anti-Defamation League. "Facebook has a moral and ethical obligation not to allow its dissemination."
Facebook only blocks Holocaust denial in four countries where it risks prosecution for letting the remarks spread, such as in Germany.
Facebook has been forced to defend itself in recent weeks for failing to take down pages that promote conspiracy theories in the interests of free speech. Pages such as Infowars have in the past promoted conspiracy theories, such as the the Sandy Hook school massacre in the US was a hoax, and yet have remained on Facebook.