Following two months of rolling strikes across the Department for Transport, the union's 8,500 DfT members will be joined by 3,500 from the Department for Environment, Food and Rural Affairs in the walkout.
Among the issues under dispute in the DfT are plans to close almost half of the UK's coastguard stations; the closure of all 39 of the DVLA's local offices and 10 enforcement centres; and cuts and the threat of privatisation in the Driving Standards Agency.
There are similar concerns over job cuts and privatisation in Defra. And all of this comes on top of a pay freeze and the looming threat of the imposition of local or regional pay, which would drive living standards down even further.
DfT members will be on strike all day and Defra members will walk out for three hours from 1.30pm.
PCS general secretary Mark Serwotka said: "Despite all the evidence pointing to the fact that austerity isn't working, this government is ploughing ahead with unnecessary and damaging cuts that will deprive our communities of vital public services."