Colin Auty, who was elected British National Party member for Dewsbury East in 2006, launched a campaign to oust BNP chairman Nick Griffin earlier this year.

But his bid collapsed just weeks after it began, with Mr Auty claiming the BNP party machine had rallied against him.

Under the extremist party's rules, he needed to get 100 signatures to challenge Mr Griffin, but failed.

He resigned his BNP membership in July, then officially left Kirklees Council at the end of last month.

A council spokesman said: "I can confirm that the chief executive has received a letter from Colin Auty informing him of his resignation with effect from August 31. A by-election will be held in due course."

Mr Auty describes himself as a "moderate," but has said his decision to resign the seat stemmed from the way people in Kirklees have treated him over his far-right activism.

He has said: "I can't get involved in projects because of my BNP badge. I get shot down by the establishment. I have met some nice people but they can't afford to be seen standing by my side."

He added that his wife had had a "rough time" for being married to a BNP councillor.

The resignation is the latest blow for the BNP in Kirklees, which it sees as a stronghold.

In last May's local elections, a concerted campaign saw trades unionist Steve Hall take a Heckmondwike seat from the BNP, for Labour.

Just one BNP councillor remains on the Kirklees authority – Heckmondwike's Roger Roberts.

Unusually, there is no mention of Mr Auty's decision to resign on the Yorkshire and Humberside news section of the BNP's official website.