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.

The move came as Gordon Brown told the GMB union conference in Blackpool that unity – along with economic recovery and political reform – was essential for Labour to recover from its drubbing in the local and European elections.

The prime minister urged trade unionists and Labour supporters to fight “like never before” to save public services. He continued to contrast the prospect of Conservative spending cuts with Labour investment, in spite of the Institute for Fiscal Studies’ warning that voters faced cuts under both parties.

Mr Prentis received a standing ovation from delegates when he called on Unison’s Labour Link section to suspend all constituency payments. Unison supports 64 Labour constituencies but gives other funding to the party.

He said the next Labour manifesto should not continue the privatisation of public services and should rebuild public provision. “We cannot tell our members to campaign and vote for a party whose manifesto promises more competition and more privatisation of our public services.”

Mr Prentis said it was no wonder that, in a Unison survey, more than 70 per cent of public service workers said they would not vote Labour.

With business backing drying up and Labour heavily in debt, the party will depend on substantial union support to fight the general election.

Unison’s move follows a threat by the Communication Workers’ Union, which gives £1m a year to Labour, to ballot its members on disaffiliation from the party if the government goes ahead with part-privatisation of Royal Mail.

Mr Brown received warm applause from the GMB delegates, although he faced tough questions after his speech on jobs, help for manufacturing and Royal Mail.

He warned: “If we don’t wake up to the problems faced by a Conservative government cutting public spending by 10 per cent, many services will be going, or gone.’’

The prime minister said he understood the anger over the MPs’ expenses scandal, adding he was determined to clean up politics, so that the “highest standards” were followed in future.

He said Britain was well placed to weather the recession, adding that no country would have recovered from the downturn if Conservative policies of doing “absolutely nothing” had been followed.

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