London Mayor Ken Livingstone yesterday launched a court appeal against a finding that he had breached a local authority code of conduct when he made a Nazi jibe to a Jewish reporter.

A three-man committee of the Adjudication Panel for England unanimously found Mr Livingstone guilty of being "unnecessarily insensitive and offensive" in comparing Jewish Evening Standard reporter Oliver Finegold to a Nazi concentration camp guard.

But James Maurici, appearing for the Mayor, told a High Court judge yesterday that the finding was "wholly untenable".

The panel decided in February that Mr Livingstone was in breach of the Greater London Authority (GLA) code of conduct and should be suspended for four weeks. The suspension order was frozen pending the outcome of the court hearing.

In court, Mr Maurici described to Mr Justice Collins how Mr Livingstone was approached, while off duty, by Mr Finegold, who was "doorstepping" a reception at City Hall marking 20 years since former Culture Secretary Chris Smith became Britain's first openly-gay MP.

Mr Livingstone asked Mr Finegold, who was accompanied by a photographer, 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.

A complaint was made by the Board of Deputies of British Jews.