A dispute over pay, jobs and terms and conditions in the Civil Service is to be escalated, with a week of strikes at the Home Office and UK Border Agency.
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, job centres, courts, museums and driving test centres.
The union said there was solid support for the strike, which it said had caused "huge disruption".
Staff at the Home Office and UK Border Agency did not join Friday's stoppage following 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 and UK Border Agency from 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. Thousands of PCS members at HM Revenue and Customs will go on strike on Monday as part of the rolling programme of action.
Mr Serwotka said Friday's action had led to job centres and other offices being closed, warning that many will shut permanently if job cuts go ahead. He accused the Government of refusing to meet the union for talks and called on Cabinet Office Minister Francis Maude to resign.
He said: "These walkouts have been very solidly supported and show the depth of anger hard-working public servants feel at having their living standards cut. We warned the Home Office and UKBA that their belligerent approach would only serve to escalate the dispute and we are now planning a longer series of strikes that will cause even more disruption."
Mr Maude said: "Our rigorous contingency plans have worked well. Throughout the day they have limited the impact of the strike significantly and as a result the majority of key public services have remained open.
"Talk of further strike action is disappointing - now is the time for us all to work together to ensure we can deliver exceptional public services, support growth and build the economy."