Ken Livingstone was facing a disciplinary inquiry last night after he refused to apologise for comparing a Jewish reporter to a Nazi prison guard.

The Board of Deputies of British Jews submitted an official complaint to the Standards Board for England, which - if upheld - could lead to Mr Livingstone being suspended or disqualified from office.

In a separate move, the London Assembly unanimously passed a motion censuring the mayor for the remarks he made last week to a reporter from the Evening Standard. Oliver Finegold had approached Mr Livingstone after a party held to celebrate the 20th anniversary of Chris Smith becoming the first MP to "come out" as a homosexual.

Mr Livingstone asked Finegold if he used to be a "German war criminal". When told that Finegold was Jewish, and that he found the remark offensive, Mr Livingstone said he was like a "concentration camp guard" because he was just following orders.

At a meeting of the assembly, Mr Livingstone defended his behaviour by claiming that Associated Newspapers, publishers of the Evening Standard and the Daily Mail, had conducted a hate campaign against him ever since his time as the Left-wing leader of the Greater London Council in the 1980s.

With his voice shaking, Mr Livingstone said: "If I could, in anything I say, relieve any pain anyone feels, I would not hesitate to do it. But it would require me to be a liar.

"I could apologise but why should I say words I do not believe in my heart? Therefore I cannot. If that is something people find they cannot accept, I am sorry, but this is how I feel after nearly a quarter of a century of their behaviour and tactics."

He was particularly critical of the Daily Mail, which he also accused of promoting "unremitting bigotry, hatred and prejudice" against various ethnic minority groups over the last 100 years.

The mayor's stance was attacked by members of all five parties in the assembly, including Labour colleagues. They said that, with the row coinciding with this week's inspection by the International Olympic Committee, Mr Livingstone could damage London's Olympic chances...