Treasury Chief Secretary Danny Alexander signalled today that ministers would stick to their guns over controversial public-sector pension reforms despite threats of mass strike action.
Mr Alexander said that millions of workers would have to pay more in contributions and work for longer if the value of their retirement benefits was to be maintained into the future.
His comments were condemned by union leaders as the "last straw", setting the stage for a wave of strikes this autumn on a scale not seen since the general strike of 1926.
Shadow chancellor Ed Balls urged unions not to fall into the Government's "trap" - accusing ministers of deliberately provoking a confrontation so they could blame them for the failing economy.
However, union leaders warned that they could not sit back in the face of such an attack on their members by the Government.
"This is the final straw," Unison general secretary Dave Prentis told Sky News's Murnaghan programme.
"Having attacked their jobs and now to take away their pensions in the way this Government is doing, it leaves them no alternative to say we're going to have to take a stand.
"We wanted to negotiate all the way through. But if we're going to be treated with disdain in the way that we are being now, then we will move to an industrial action ballot.
"And it will be the biggest action since 1926 because up to 10 million people will be involved."
His warning was echoed by Mark Serwotka, the general secretary of the Public and Commercial Services Union (PCS) representing civil servants, whose members have already voted to join teachers in a day of action on June 30.
"I think if the Government isn't prepared to change course in the negotiations that we are having after that strike, we will see unions representing millions more move to ballot their members for strikes in the autumn," he told BBC1's The Andrew Marr Show.
Mr Alexander insisted that ministers wanted a "constructive dialogue" with the unions - but indicated that this would be restricted to the detail of how the changes would be implemented.
He made clear that the Government was determined to stick to the broad principles for reform set out in the review of public-sector pensions carried out by former Labour cabinet minister Lord Hutton.
"They are the basis on which we want to go forward and reform public-service pensions, but of course in these discussions we need to look at the detail of how that works, about how these things are implemented," he told the Murnaghan programme.
"What we have to get to is a situation where, yes, people have to work a bit longer and contribute a bit more, as we have put forward, but that we maintain the quality of their pensions into the future."
Mr Alexander repeated his warning that it would be a "colossal mistake" for the unions to go ahead with the strike on June 30 while negotiations were still continuing.
However, Mr Balls claimed that Chancellor George Osborne was deliberately trying to engineer a confrontation with the unions to deflect attention from the continuing poor performance of the economy.
"George Osborne is desperate to have that confrontation. He has been saying it for months," he told The Andrew Marr Show.
"The trade unions must not walk into the trap of giving George Osborne the confrontation that he wants to divert attention from a failing economy."
He warned that the public did not want a return to the "massive strikes and confrontation" of the 1980s.
But, at the same time, he said the Government's proposals were unfair and called on ministers to think again.
"If you are a man or woman in your early 50s who has worked in the public services for 20 or 30 years, the idea that you suddenly find out you may have to wait years longer to get the pension you believe you are entitled to, I think most people would say that is really unfair," he said.
"That is why the Government has got to look at this again."Reuse content