Tension between Labour and its trade union backers deepened on Tuesday when the leader of one of the biggest unions announced moves to suspend funding to local Labour parties, saying his members were tired of “feeding the hand that bites them”.

Dave Prentis, general secretary of Unison, said there would be no more “blank cheques” for Labour and that the union’s payments to constituencies should be suspended. Unison would only support prospective Labour candidates willing to stand up for its values of public service, he told the union’s annual conference in Brighton.