A quarter of a million civil servants are to join striking teachers for a mass walkout on 30 June, bringing schools, colleges, universities, courts, ports and job centres to a halt.
Up to 750,000 state employees are expected to take part in the strike, over the government's pension reforms, after the PCS union's ballot backed rolling strike action by 61%.
Mark Serwotka, the general secretary of the PCS, said the action was principally against cuts but also against the coalition's public service reforms.
"The clear majority in favour of a strike shows that public servants – who provide vital services across the country – are not prepared to stand back while everything they have ever worked for is taken from them," he said.
"The government claims this is about rebalancing pensions, but it has already admitted that the money it saves will go straight to the Treasury to help pay off the deficit in what amounts to nothing more than a tax on working in the public sector.
"I have been at every one of the negotiating meetings with the government, and what we've been told is that they won't budge on increasing the pension age, they won't budge on their plans to double or triple contributions, and they won't budge on the value of our members' pensions being slashed.
"In reality, the talks are a farce and, faced with mass job cuts, the pay freeze and the biggest raid on pensions in living memory, it's not surprising that people want to defend themselves."
Francis Maude, the Cabinet Office minister, has repeatedly called on the unions to await the outcome of the pensions talks that are currently under way before striking, calling those going ahead with industrial action "irresponsible and wrong".
But on Wednesday, it emerged that a second headteachers' union, the Association of School and College Leaders, was also moving towards a ballot for strike action.
Three teachers' unions – the National Union of Teachers, the Association of Teachers and Lecturers and the Universities and College Union – have all said they will strike this month.
Nearly every major public sector union has now indicated that it is likely to ballot once the talks conclude this summer. Insiders say negotiations are all but at a stalemate, with ministers and unions failing to agree on even basic principles.
It means there could be rolling strike action across the public sector in the autumn, which could profoundly disrupt the work of the state.
Maude told MPs during Commons questions that "rigorous contingency plans" were in place should a walkout go ahead.
He said: "We are engaging in discussions with the TUC at the behest of the TUC – those discussions are continuing. There's much still to be sorted out.
"It was Lord Hutton, the previous Labour pensions secretary, who recommended these reforms to make public sector pensions schemes sustainable and affordable for the future. That's what we're determined to achieve.
"Any union or any public servant contemplating strike action at the moment is really jumping the gun – there's a long way to go on this yet."
He added: "I am sorry that a handful of unions are hell-bent on pursuing disruptive industrial action while those discussions are still continuing, though we have rigorous contingency plans in place to minimise disruption in the event of industrial action."