The leader of one of the country's biggest unions today 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, adding that payments from the union to constituencies should be suspended.
Unison will only support prospective Labour candidates willing to stand up for its values of public service, he told the union's annual conference in Brighton.
He received a standing ovation from delegates when he called on the union's Labour Link section to suspend all constituency payments.
"Our people are crying out for change. But it's not about personalities. It's not about who's got the X-factor, or the nicest smile.
"It's about the policies this government and previous governments have pursued. Policies that are an anathema to the values of our union - values of social justice, public service, solidarity, responsibility, public accountability.
"Policies that have taken our economy in the wrong direction.
"Policies that are damaging our public services.
"Our public finances have been plunged deep into the red as the Government has spent trillions protecting the economy from the reckless profiteering of the private banking sector.
"The very same Government says the solution is to hand larger and larger chunks of our public services over to private companies that will always put profit before public interest. Absolute lunacy."
Mr Prentis said it was no wonder that a Unison survey had discovered that for the first time ever, more than 70% of public service workers now said they wouldn't vote Labour.
"Despite the collapse in support from pubic service workers, what is being proposed months away from an election? A privatisation of our NHS more radical than anything our members saw, even in the dark days of Thatcher. Market testing of all NHS services.
"A new competition panel to provide redress to those private companies who don't think they're given a fair chance."
Mr Prentis said the next Labour manifesto should not continue the privatisation of public services, arguing it 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."
Unison supports 64 Labour constituencies but gives other funding to the Labour party.
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