Unite, Britain's biggest union, has voted by three to one in favour of joining a mass day of action on 30 November over plans to cut public-sector pensions.
The National Association of Probation Officers also announced it would be staging a national strike, for only the third time in its 100-year history. The GMB and local government and health workers at Unison have already announced support for the action which is expected to involve two million workers – the biggest show of industrial strength since the winter of discontent in 1979.
The largest teachers' union, the NASUWT, is expected to announce the results of its strike ballot in England and Wales today. The National Association of Head Teachers last week voted to strike for the first time in 114 years.
Unite's general secretary, Len McCluskey, said public-sector workers "have endured wages cuts, rising living costs and horrific job losses, as this Government forces the less well-off to pay for the sins of the elite. They are not prepared to stomach this attack on their pensions too."
The Government has already made concessions on its plans to raise the retirement age and increase employee contributions.