Andy Gilchrist has been toppled as leader of the Fire Brigades Union by a left-wing candidate.
Matt Wrack beat Gilchrist, who had been general secretary of five years, in a union leadership ballot. Wrack polled 12,833 votes with Gilchrist receiving 7,259 in a turn-out of 20,000 firefighters.
Gilchrist led the bitter national strike over pay and restructuring.
Commentators now say the vote could start a new set of rows with the government.