Civil servants are to stage a strike on Budget day to launch three months of industrial action in a worsening row over pay, pensions and working conditions.
The Public and Commercial Services union said almost 250,000 workers will take part in a rolling series of walkouts and protests as it steps up its campaign against cuts.
A 24-hour strike will be held on 20 March, the day Chancellor George Osborne presents the Budget to Parliament.
Further national stoppages will be held, of varying durations and targeting different parts of the civil service, with dates to be announced at a later stage.
Other forms of disruptive industrial action short of a strike will also be held, and the PCS said it will seek to co-ordination with other unions on pay and pensions.
PCS general secretary Mark Serwotka said: "This is not a one-day protest, this is the start of a rolling programme of walkouts and disruptive action to put pressure on a government that is refusing to talk to us.
"Civil and public servants are working harder than ever to provide the services we all rely on but, instead of rewarding them, the government is imposing cuts to their pay, raiding their pensions and trying to rip up their basic working conditions.
"We warned more than two years ago that austerity wouldn't work and we were right. There is an alternative to cutting the living standards of hard-working public servants and our campaign is designed to make the case loud and clear."
A Cabinet Office spokesman said: "It is disappointing that, yet again, the PCS insist on pushing for futile action which benefits no-one, and damages the services they deliver to the public.
"The Government took the tough decision to freeze public sector pay for two years, while protecting those earning under £21,000 by increasing their pay by at least £250 per year. Pay restraint has helped to protect jobs in the public sector and support high- quality public services.
"In March 2012 we set out our final proposed agreements on pension reform following more than a year of intensive discussions with trades unions. These reforms will ensure that public sector pensions will remain among the very best available and that they can be sustained for future generations.
"Because we want to attract the best staff, we will remain an employer with good terms and conditions, as we have always been. However, while there has been significant recent change in pay and pensions, there are other terms and conditions that have not been updated. We will address this and ensure a modern employment offer is available to all."
The PCS said its officials will meet weekly during the industrial action campaign to track progress and decide tactics, with decisions on a second phase taken after the union's annual conference in mid-May.
PCS members at the Department for Education will stage a two- hour strike tomorrow afternoon in protest at planned job cuts.