Thousands of jobs are under threat after the Government's biggest department announced plans to close a number of Jobcentre Plus offices, union leaders warned.
The Public and Commercial Services union (PCS) said 17 benefit-processing sites and five contact centres will be shut, mainly over the next year, affecting 2,400 posts.
The Department for Work and Pensions (DWP) said staff affected by the decision will be offered jobs elsewhere, adding that the announcement was about "buildings, not people".
But the union said there was "absolutely no way" jobs could be found for all those hit by the move, which it described as "deeply flawed and dangerous".
PCS officials said the closures were coming at a time when hundreds of thousands of public sector workers were losing their jobs as a result of the Government's spending cuts.
A DWP spokesman said: "All staff affected by this will be offered jobs elsewhere in the organisation. This is about buildings, not people - we simply can't afford to carry on paying for buildings which aren't fully used. In tough financial times, we have to operate as efficiently as possible. Frontline Jobcentre Plus services aren't impacted by this and benefit payments won't be affected."
Jobcentre Plus has already axed more than 10,000 jobs since 2009, said the union, warning that the latest losses will lead to further delays in processing claims.
PCS general secretary Mark Serwotka said: "This is a deeply flawed and dangerous plan that will remove vital support to jobseekers and people claiming welfare at precisely the time the Government's ideological cuts will throw more people out of work. Instead of cutting jobs, the Government should be investing in public services like these to help get people back to work more quickly and help our economy to get back on track."
The union's annual conference next week is set to launch a campaign against spending cuts, including the jobcentre closures. Delegates are expected to agree to hold a ballot for nationwide industrial action by civil servants, which could be co-ordinated with other groups of public sector workers, including teachers.
The PCS said it had been told that offices earmarked for closure were at Arbroath, Ayr, Broadstairs, Caerphilly, Cannock, Carlisle, Castleford, Chester, Clydebank, Exeter, Grimsby, Halifax, Hartlepool, Huyton (Merseyside), Lincoln, Liverpool John Moores, Luton, Mansfield, Preston, Sutton in Ashfield, Totton (Southampton) and Yeovil.