Mr Mason, who represents Cosham on Portsmouth City Council, has been suspended by his local Portsmouth North Conservative Association pending the results of an investigation.
The photo, which shows five buns, was leaked to the The News and also included what the Councillor described as an Scottish National Party emblem.
The Campaign Against Antisemitism condemned Mr Mason and called for an immediate investigation.
It said: “Next week, the Jewish community will be observing Yom HaShoah, remembering the six million Jewish men, women and children slaughtered during the Holocaust just for being Jewish.
“The Jewish community and local residents in Portsmouth expect better from their representatives. The Conservative party must investigate this councillor’s conduct immediately.”
Labour's Portsmouth South MP Stephen Morgan condemned the hot cross buns, saying: “At a time when our whole community is pulling together to support each other, anything suggesting the use of the most offensive of symbols is shockingly inappropriate and shameful.”
He also noted that the Councillor may face the prospect of an investigation by the City Council.
“If true, it may also breach the members' code of conduct. It is only right that serious and legitimate concerns be reported to the city council under its complaints system for councillors,” he continued.
Mr Mason served as the Lord Mayor of Portsmouth, alongside his mother and Lord Mayoress Sylvia, between 2018 and 2019.
