Peter Davies was elected to run Doncaster Council as a member of the English Democrat Party, which describes itself as a nationalist party campaigning for an English parliament.
But yesterday Mr Davies, held up as an example to others by English Democrat chairman Robin Tilbrook, said he could no longer remain in the party.
Mr Davies said he had been made aware of an event attended by leading members of the English Democrats which was also attended by far-right groups such as the English Defence League. He said he was also concerned about recent claims that ex-members of the British National Party had joined the English Democrats, which he said was “appalling”.
The mayor, who is standing for re-election in May, said he was now considering his next move although added it was unlikely he would stand as an independent.
But he added: “I will certainly not be joining any of the main three parties because we have got a situation at the moment where you can’t get a cigarette paper between them. They do not represent ordinary people.
“What I can say is nothing will change in Doncaster. Having been privileged to hold this office I have tried to meet the economic and social needs of the people of the town and that will continue.
“I believed I was joining a moderate party calling for fairness for all nations of the British Isles. For me, fairness for Doncaster and its people is paramount. I have raised my concerns with party leaders, but it has had no impact.”
Mr Tilbrook said the Doncaster mayor had “misread” the situation and his party would be fielding a candidate in Doncaster.