British trade unions representing millions of workers were giving notice of plans for ballots on a series of one-day national strikes this autumn if the government does not negotiate on rises in public-sector pensions, union sources said.
Dave Prentis, head of the second largest union, Unison, said he was notifying 9,000 employers immediately that 1.1 million members would voting on industrial action.
He said the ballot was "unprecedented in scale" and would cover millions of workers in health, local government, schools, universities, the police and the private sector.
"It's a decision we don't take lightly. And the stakes are high. Higher than ever before. Now is the time to make our stand," he told delegates on the final day of a conference organised by the Trades Union Congress (TUC) in London.
Two other big unions, Unite, representing 1.5 million public sector workers, and the GMB, with 600,000 members, were expected to follow suit, union sources told Reuters.
They join two civil service and one teaching union who have already declared their intention to ballot members over pension reforms which they say are equivalent to a tax on the lowest paid workers.
The TUC is an umbrella labour organisation made up of 58 unions representing almost 6.5 million workers -- a quarter of Britain's work force.