London Mayor Mr Ken Livingstone has refused to apologise to the Jewish reporter he likened to a Nazi concentration camp guard.
However, Mr Livingstone told the capital's Jewish community he did not mean to offend them.
At a City Hall press conference, Mr Livingstone said he had been deeply affected by the concern of Jewish people following his remarks to Mr Oliver Finegold two weeks ago.
"My words were not intended to cause such offence," he said. Mr Livingstone said that after a week of reflection he had decided: "There will be no apology or expression of regret to the Daily Mail group."
He accused Mr Finegold of "unacceptable behaviour", pursuing him along the pavement and "barking" the same question at him. He said that if the reporter had been offended by his remarks he was "in the wrong job".
He went on: "To the Daily MailI say no one in Britain is less qualified to complain about anti-Semitism."
He said the group's newspapers had been "leading advocates of anti-Semitism in this country for half a century".
His only expression of regret was to London's Jewish community. Mr Livingstone said: "I've been deeply affected by the concern of Jewish people in the city, in particular that my comments may have been seen to downplay the horror and magnitude of the Holocaust.
"I wish to say to Londoners my words were not intended to cause such offence." A formal investigation has been opened into Mr Livingstone 's jibe to Mr Finegold.
The Standards Board for England, the local government watchdog, is considering whether the Labour mayor breached the Code of Conduct of the Greater London Authority.
If Mr Livingstone is found to have failed to treat others with respect, he could face a range of punishments including being barred from office for five years.