London Mayor Ken Livingstone is to face a charge of bringing his office into disrepute over comments he made to a Jewish journalist.
Mr Livingstone said his words were not intended to cause offence
The mayor was caught on tape comparing the reporter to a "concentration camp guard", outside a party in February.
The disciplinary panel, sitting for a second day, could, at worst, ban him from office if he is found guilty.
On Tuesday, his lawyers failed to have the case thrown out - but did get one of two charges against him dropped.
The charge that the mayor failed to treat others with respect was dismissed, because it only applies to those acting in an official capacity.
The three-man panel ruled Mr Livingstone had been acting as a private individual during the conversation with Evening Standard reporter Oliver Finegold after an official reception at City Hall in February.
The case was brought against him by the Standards Board of England to decide if he had breached his office's code of conduct.
If so, he could be ordered to apologise, banned from office, suspended, censured or told to go for training.
The mayor refused to apologise to Oliver Finegold
Speaking on Tuesday, Mr Livingstone said: "We're still in a position where tomorrow I could be suspended from office or barred for five years.
"I don't want to say anything to upset them in the next 24 hours."
Following the confrontation between Mr Livingstone and Mr Finegold outside a party for MP Chris Smith, the Mayor refused to apologise to the reporter.
He said he was the victim of a 24-year hate campaign by Associated Newspapers, publishers of the Evening Standard and the Daily Mail.
But he said his words were not intended to cause such offence.
The case is being heard at the Aeonian Centre in central London.