The PCS union said its members voted to take action on 28 April to increase the pressure on the government and were "not backing down".

PCS general secretary Mark Serwotka said: "Ministers need to resolve the dispute by putting money on the table."

The government said their demands would cost an "unaffordable £2.4bn".

Urging the PCS union to call off the strikes, a spokesperson said the government's focus was to "ease the pressure on households across the country" as the cost of living soars.

"That is why public sector pay awards strike a careful balance between recognising the vital importance of public sector workers, while delivering value for taxpayers and avoiding higher prices in the future," the government spokesperson added.

Members of the PCS union, who have been offered a 2% to 3% increase, last walked out on Budget day earlier this month.

The PCS union represents hundreds of thousands who work in government departments as well as those at organisations such as Ofsted, the Maritime and Coastguard Agency and Border Force.

It has been calling for a 10% pay rise, better pensions, job security and no cuts to redundancy terms.

Mr Serwotka said: "We know our strikes have already caused serious disruption. The new strikes and another national day of action will pile the pressure on a government that refuses to listen."

The union said the all-out strike on 15 March was "brilliantly" supported by members, with big picket lines and demonstrations.

Teachers, junior doctors, rail workers and London Underground tube drivers are some of the industries whose workers have walked out in disputes - mainly over pay - over the last year as wages do not align with the rising cost of living.

One of the biggest days of strikes was whilst Chancellor Jeremy Hunt deliver his Budget, with workers congregating around Westminster.

Members from 186 different employers were balloted over the latest strike action last week, the PCS union said.