The government announced that pay rises would be limited to 4.5% to 5%, which according to the Public and Commercial Services Union (PCS) is an "insult."
"Our members are on strike today because they are very angry that the government seems to have singled out its own workforce for the worst treatment of anybody in the public sector or across the British economy," said PCS General Secretary Mark Serwotka.
The government employees were only given a 2% pay increase last year, the lowest among all public sector workers, he said.
"It has only offered 4.5% in 2023, its own workforce are the only workers they are not negotiating with and we are the only part of the public who have not been offered any backdated pay award or lump sum to compensate for the chronic cost-of-living crisis," he added.
"And we’re determined to keep going on strike until the government recognizes its own workforce and pays them a decent wage."
The PCS union members have been engaged in a series of strikes for several months, demanding a significant pay rise of 10%, along with improved pension benefits, job security, and the preservation of redundancy terms without any cuts.
Food inflation in the UK hit a 45-year high of 19.1% in March. There was, however, a drop in the annual consumer prices index to 10.1% in March from 10.4% in February.
According to the schedule on the union website, industrial action will continue on specific days until at least June 2.