More than 6,000 Jobcentre staff are to go on strike today in a long-running dispute over "oppressive working conditions and unrealistic targets".
Members of the Public and Commercial Services (PCS) union in 32 call centres in England, Scotland and Wales will reignite industrial action first taken last year.
They claim that "draconian" conditions are preventing them from providing a decent service.
PCS general secretary Mark Serwotka said: "With unemployment remaining high and our economy in the grip of recession, it is shameful that Jobcentre bosses are still refusing to let their staff provide the kind of help and advice that people need.
"These call centres provide a vital lifeline. Inquiries are often complicated, and people struggling to find their way around the benefits system are often understandably desperate and upset, but staff are being forced to end calls as quickly as possible just to meet an artificial target.
"Our members care about the services they provide and they want to be able to help people properly, not have to fob them off."
The union said Jobcentre bosses were only interested in getting claimants off the phone rather than dealing with their inquiries properly.
A Department for Work and Pensions spokesman said: "We are disappointed that some staff are taking industrial action which we think is unnecessary. We have gone to great lengths to resolve issues with unions.
"Jobcentres and benefit payments will be unaffected and claimants will be able to access some information online, so any impact will be limited."