Thousands of workers at the DVLA and Transport Department are striking on Friday, as part of the long-running dispute over jobs, office closures and pay.
Between 2pm and 5pm, Swansea and south Wales based members of the Public and Commercial Services union (PCS) will walk out, in the latest in a series of protests.
The PCS has said more than 1,200 jobs at the DVLA are threatened under plans to close offices and transfer work to the agency's headquarters in Swansea.
PCS industrial officer Mike Hallinan said: "The number of jobs that could transfer to Swansea is unconfirmed. Many of them may prove to be temporary and the ongoing cuts programme makes it highly unlikely that there will be any net increase in staffing in Swansea.
"Most importantly, of course, these would not be new jobs at all, but the transfer of work from hard-working public employees whose future is now in jeopardy.
"Our members will be taking action tomorrow in opposition to the department's whole programme of cuts, closures and privatisation. We believe that the Government should not be making public sector workers bear the burden of an economic crisis they didn't create."