The Home Office is to be hit by a week of strikes in an escalation of a campaign of industrial action in a row over pay, jobs, terms and conditions.
The move was announced as tens of thousands of members of the Public and Commercial Services union staged a half-day walkout from Government departments, jobcentres, courts and driving test centres.
A planned strike by staff at the Home Office and UK Border Agency was called off after a legal challenge by the Government.
But PCS general secretary Mark Serwotka told a rally outside the Cabinet Office in Westminster that a week of strikes will be launched at the Home Office from a week on Monday (April 15), with different groups of workers taking action at different times.
The strikes are part of a three-month long campaign of industrial action, which started with a stoppage on Budget Day last month.
Mr Serwotka said today's action had been solidly supported, adding that jobcentres and other offices had been closed.
He accused the Government of refusing to meet the union for talks and called on Cabinet Office minister Francis Maude to resign.