Ken Livingstone's political career was rocked yesterday when he was suspended as Mayor of London for making a Nazi jibe to a Jewish reporter.

Barring a possible last-ditch appeal to the High Court, the mayor will begin a four-week suspension on Wednesday for bringing his office into disrepute.

A three-man disciplinary tribunal unanimously ruled that Mr Livingstone was "unnecessarily insensitive and offensive" when he compared the London Evening Standard's Oliver Finegold to a Nazi "concentration camp guard".

Not only has the case been damaging to Mr Livingstone's reputation, it will also hurt his pocket, as he now faces a bill for legal costs which tops £80,000.

"This decision strikes at the heart of democracy," he said. "Elected politicians should only be able to be removed by the voters or for breaking the law.

"Three members of a body that no one has ever elected should not be allowed to overturn the votes of millions of Londoners."

The Adjudication Panel for England ruled that Mr Livingstone broke the Greater London Authority's code of conduct when he clashed with Mr Finegold in February last year.

Panel chairman David Laverick said: "His treatment of the journalist was unnecessarily insensitive and offensive.

"He persisted with a line of comment likening the journalist's job to a concentration camp guard, despite being told that the journalist was Jewish and found it offensive to be asked if he was a German war criminal."

Mr Laverick added: "Matters should not have got as far as this, but it is the mayor who must take responsibility for this.

"It was his comments that started the matter and thereafter his position seems to have become ever more entrenched."

Trouble flared as Mr Livingstone was approached, while off duty, by Mr Finegold as he left a party marking 20 years since former Culture Secretary Chris Smith became Britain's first openly-gay MP.

Mr Livingstone asked Mr Finegold whether he had ever been a "German war criminal". On hearing that Mr Finegold was Jewish, the Mayor likened him to a Nazi concentration camp guard.

The panel was told Mr Livingstone had been expressing his long and honestly held political view of Associated Newspapers, publishers of the Daily Mail and the Evening Standard.

Mr Livingstone accused Associated Newspapers of a history of anti-Semitism and the Evening Standard of "harassing" the largely gay private reception, paid for from public money.

In the storm which followed, Mr Livingstone said he was using his freedom of expression and had never meant offend the Jewish community or downplay the Holocaust.

Calls are now growing for Mr Livingstone to apologise.