The Government is facing a legal challenge to its controversial decision to introduce "brutal" charges of around £1,000 to take an employment tribunal case, it has been revealed.
Unison has applied to the High Court for a judicial review in a bid to stop the new fees, which are due to come into force next month.
General secretary Dave Prentis announced the move at Unison's national conference in Liverpool, adding that the union will pay its members' tribunal fees up front, whether they win a case or not.
He launched a scathing attack on the Government's policies, but also had harsh words to say about Labour, warning that Unison would not support a Labour administration that did not end privatisation or restore workers and union rights.
"For far too long we've built the careers of Labour politicians, only to be let down when we needed them most. I don't want to hear Labour apologising for their past mistakes."
He drew loud applause from delegates when he urged shadow chancellor Ed Balls to decide which side he was on, adding: "Cutting welfare and rivalling Tory spending cuts may win you support in the right-wing press, but it won't win you the last election."
Mr Prentis said he had some advice for Labour leader Ed Miliband, repeating the words of Nye Bevan: "We know what happens to people who stay in the middle of the road - they get run over."
Mr Prentis reserved his strongest attacks for the coalition, saying that workers were in the "eye of a storm" because of the Government's policies.
"The Tories are using the recession to destroy our welfare state, with no price too high for our people to pay. A scorched earth policy of welfare and spending cuts to shrink our state beyond repair.
"Wages are in freefall, except for those who caused the crisis in the first place, our public services are being savaged and politicians talk about austerity when they mean cruelty and vindictiveness."