PlayUN diplomats have walked out of a speech in protest at comments delivered by Iranian President Mahmoud Ahmadinejad.
Delegates at the racism conference in Geneva disrupted Mr Ahmadinejad's speech when he claimed the Israeli Government is racist against Palestinians.
One heckler, wearing a rainbow-coloured wig, was bustled out of the conference room. But his comments drew applause from some delegations that remained.
Ahmadinejad, who has in the past cast doubt on the Nazi Holocaust, accused Israel of occupying Palestinian territories "on the pretext of Jewish suffering".
Britain and the US were among eight Western states which decided not to send a minister to the meeting over concerns that it would be used as a platform for criticism of Israel.
But British ambassador Peter Gooderham was in attendance and he said: "Such outrageous anti-Semitic remarks should have no place in a UN anti-racism forum."
French ambassador Jean-Baptiste Mattei said: "It is a pity that Mr Ahmadinejad is trying to take this conference hostage. We are ready for serious discussion but this is beyond what should have been expected."
Mr Brown's spokesman said: "The view of the British Government is that we unreservedly condemn the Iranian President's offensive and inflammatory remarks.
"Such remarks have no place anywhere, least of all in a UN anti-racism forum."
He added: "We don't think that the President of Iran's presence in itself constituted grounds to withdraw from the conference, but in the light of his remarks the decision was taken that we would not attend for the part of the speech in which he was speaking."
Meanwhile, US Secretary of State Hillary Clinton has called for the "speedy release" by Iran of imprisoned Iranian-American journalist Roxana Saberi, who has been sentenced to eight years in jail on spying charges.
"She has been subjected to a process that has been nontransparent, unpredictable, arbitrary," Mrs Clinton said.
"We hope that actions will be taken as soon as possible by the authorities in Iran, including the judiciary, to bring about the speedy release of Miss Saberi and her return home."
© Independent Television News Limited 2009. All rights reserved.
