Staff working at three Universal Credit centres are to be balloted for strike action in a dispute over staffing levels and workloads.
Members of the Public and Commercial Services Union (PSC) in Wolverhampton, Walsall and Stockport will vote on whether to launch a campaign of industrial action.
The union said workers at the contact centres were angry about their caseloads increasing while the number of staff was reduced, making it "impossible" for them to adequately support claimants.
A Department for Work and Pensions spokesperson said: "Planned meetings with the union are ongoing and our priority is ensuring there is no disruption to our customers.
"Our front-line staff deliver vital support to around 20 million people across the country and we are committed to supporting them in their roles, including by monitoring staff levels and making sure their caseloads are manageable."