Civil servants are to follow up a strike on Budget day with a second walkout in a row over pay, pensions and terms and conditions.
The Public and Commercial Services union said almost 250,000 members who work in government departments and its related bodies will hold a half-day walkout on April 5, the end of the tax year.
The union has called a 24-hour stoppage on Wednesday to coincide with the Budget after accusing the Government of refusing to negotiate over cuts.
PCS general secretary Mark Serwotka said: "We will quickly follow up our budget day strike with a walkout on April 5 and step up our campaigning for the Government to take serious action against wealthy tax dodgers. With polls showing people are less likely to support government policies if George Osborne's name is attached, it is clear the public have lost faith in austerity and want an alternative."
The union is planning a three-month programme of industrial action and a fresh campaign against tax avoidance and evasion.
Ministers are being urged by the Treasury to scrap decades-old civil service pay arrangements that allow staff to progress from minimum starting levels up a series of pay bands within their grade, the PCS said.
"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 and are now outliers compared to best practice. We will address this and ensure a modern employment offer is available to all."