Civil servants in government departments, driving test centres, museums and galleries will stage a 24-hour strike on Budget day in a bitter row over pay, pensions and working conditions.
The Public and Commercial Services union (PCS) said up to 250,000 of its members will join the walkout, which will also hit jobcentres, tax offices, border patrols at ports and airports, and courts.
All business in the Welsh Assembly has been cancelled because Labour and Plaid members will not cross a picket line.
The union has also called a half-day strike on April 5 as part of a three month long campaign of action.
Picket lines will be mounted outside government offices, museums, galleries and the Houses of Parliament. A rally will be held in Westminster while the Budget is being delivered by Chancellor George Osborne.
The union has been embroiled in a long-running dispute with the Government over pay and pensions, which worsened when the PCS accused ministers of attacking working conditions of civil servants.
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. 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."
The union, which also represents staff in the passport agency, Metropolitan Police, coastguard stations and Parliament, accused ministers of refusing to negotiate.
Unite members at the Homes and Communities Agency (HCA) are also striking over pay.
Cabinet Office minister Francis Maude condemned the strike as "futile, counterproductive and irresponsible".
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