Andrew Brons, the MEP for Yorkshire and the Humber, has resigned from the British National Party (BNP).
Mr Brons, who led the National Front in the 1980s, resigned after a dispute with current BNP chairman and MEP, Nick Griffin.
Mr Brons, 68, said: “The current chairman of the rump BNP has described me in a text to his attack dogs as ‘vermin’.
"More recently, he described me as a ‘state agent’ – a description he attached to me 26 years ago but which obviously did not apply when he appointed me as the lead candidate in Yorkshire for the European elections.
“I was elected because I headed a party list and not because of any personal qualities recognised by the electorate.”
Mr Brons was a member of the neo-Nazi National Socialist Movement and co-edited the New Nation journal with Holocaust denier Richard Verrall.
The far-right has been characterised in recent years by a series of fractious in-fights, resignations and allegations of corruption. It is not clear under what party banner Mr Brons will continue to sit in the European Parliament.