The PCS union plans a second walkout as the row with the government over pay escalates.
About 100,000 civil servants are set to strike on the day the chancellor unveils the Spring Budget, the Public and Commercial Services union has said.
Mark Serwotka, general secretary of the PCS, said members would walk out on 15 March as part of an ongoing row with the government over pay and conditions.
The PCS has been calling for a 10% pay rise, better pensions, job security and no cuts to redundancy terms.
The government has been contacted for comment.
The PCS represents thousands of workers who work in government departments as well as workers at organisations such as Ofsted, the Maritime and Coastguard Agency, and Border Force.
The union said its members from 123 government departments would take part in the industrial action, which include staff at the Department for Education, Department of Health and Social Care and the Home Office.
Some 100,000 civil servants previously walked out on February 1.
Mr Serwotka said PCS members were “suffering a completely unacceptable decline in their pay”.
“Rishi Sunak doesn’t seem to understand that the more he ignores our members’ demands for a pay rise to get them through the cost-of-living crisis, the more angry and more determined he makes them,” he said.
He said the prime minister could “end this dispute tomorrow if he puts more money on the table”.
“If he refuses to do that, more action is inevitable,” Mr Serwotka added.
The Spring Budget in March will see Chancellor Jeremy Hunt, who is in charge of the government’s finances, outline to the House of Commons his plans for taxation and spending.
The government has previously offered civil servants a 2% to 3% pay rise, but union bosses have been calling for a rise of 10%, a similar level to the rate of overall inflation in the UK, which is at a 40-year high.
Price rises have been squeezing household budgets and there has been a wave of strikes across the UK in sectors ranging from healthcare to railways in recent months.