The call follows the announcement that HMRC has agreed staff will be able to work from home two days a week.
The new flexible working policy is expected to come into operation from 1 June.
According to PA, prime minister Boris Johnson insisted earlier this month that the government’s work from home advice is set to be dropped on 21 June, telling MPs that UK cities depend on “people having the confidence of going to work”.
But HMRC said it wanted to “recognise the benefits of smarter ways of working” in its new pay and working reforms.
PCS has a default position that civil servants work from home where they can and five tests for safe working, where going into the workplace is essential.
Once it is safe to return to the workplace, PCS will be demanding the civil service takes a flexible approach to office work and liaises with staff and union representatives to decide what is best for both safety and the individual needs of workers.