London mayor Ken Livingstone will face a disciplinary hearing for comparing a Jewish journalist to a Nazi concentration camp guard.
The independent Adjudication Panel for England could ban the mayor from office for up to five years if it rules against him.
The hearing follows an inquiry into an incident at a party in February, where Mr Livingstone accused the reporter of "doorstepping" him.
The mayor will appear before the panel by December over allegations that he brought his office into disrepute and that he failed to treat others with respect.
If the panel finds that the mayor breached the Greater London Authority (GLA) Code of Conduct, he could be suspended, censured, ordered to apologise or to go for training.
But a five-year ban from office is thought to be unlikely.
A tape recording of the confrontation outside a party for MP Chris Smith captured the mayor asking Evening Standard reporter Oliver Finegold if he was a "German war criminal".
Mr Finegold replied: "No, I'm Jewish, I wasn't a German war criminal. I'm quite offended by that."
The mayor then said: "Ah right, well you might be, but actually you are just like a concentration camp guard, you are just doing it because you are paid to, aren't you?"
Mr Livingstone kept refusing to apologise, saying that he did not mean to offend Jews.
Instead he claimed Associated Newspapers, owners of the Evening Standard and the Daily Mail, had persecuted him and his family for 24 years.
The Board of Deputies of British Jews complained to the Standards Board of England, which has now referred the matter to the independent panel.
The Standards Board said in a statement it could not hand over the case to the GLA's own standards committee, as its members had "already expressed a view on the issue".
Yet Graham Tope, Liberal Democrat leader at the London Assembly, said: "It is unfortunate that this whole sordid sorry little episode has had to go to the Adjudication Panel for England when the Mayor could have eaten some humble pie and said sorry."
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