His comparison of Finegold's behaviour to that of a concentration camp guard was deemed "unnecessarily insensitive" by the Adjudication Panel for England. Finegold had allegedly been "doorstepping" Livingstone outside a party when the politician made the comment.
Livingstone's lawyer argued that there was no evidence that the mayor had damaged his office with his remarks. However, the tribunal rejected his argument.
The hearing followed a complaint made by the Jewish Board of Deputies. Livingstone's suspension is due to begin on March 1, although it is believed he may appeal the ruling to the High Court.
David Laverick, chairman of the three-man disciplinary panel, said: "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."
Livingstone defended his comments on the basis they reflected his political views on the Evening Standard's publisher Associated Newspapers.
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