Disabled workers at factories being sold by the Government are to stage a four-day strike over the threat of job losses.
Members of the GMB and Unite unions at Remploy sites in Chesterfield and Springburn, Glasgow, will walk out from August 28.
Officials accused the Department for Work and Pensions (DWP) of removing the obligation for a new employer to provide a pension, and warned that potential buyers may want to make redundancies based on an individual's disability.
GMB national officer Phil Davies said: "Members are concerned that no information about three potential buyers has been given to them. The DWP has removed the obligation for a new employer to provide a pension.
"We understand that all three potential buyers may want to make redundancies based on the individual disability."
The GMB said 25 Remploy factories closed last week under controversial Government plans to switch spending to help individual workers find jobs in mainstream sectors.
Kevin Hepworth of Unite said: "To attack the most vulnerable in our society and throw them on the scrap heap is an act against disabled people."
Half of Remploy's 54 factories are to close by the end of the year, 18 will close or be sold next year and the remaining nine face an uncertain future.
A DWP spokesman said: "We're disappointed that the unions are taking more strike action which will do nothing to secure the future jobs of Remploy staff.
"The Government would encourage the trade unions to fully engage with Remploy during the current process to provide the best possible support and success for disabled staff who may leave the company."