Trade unions say they are furious that six leading charities have backed plans to close dozens of factories which provide jobs for disabled people.
In March, Remploy workers protested in Cardiff against closures
Remploy, which has 5,000 disabled staff at 83 plants in the UK, says it has to cut costs.
Charities including Mencap and MIND support the closures, insisting that disabled people should be given jobs in mainstream industries instead.
Set up in 1945, Remploy receives £111m in government subsidy every year.
It says it has to close factories to avoid going over budget.
Phil Davis, national secretary of the GMB union, said: "Disabled people have had to fight all their lives for where they are. These people will not go away quietly."
And he insisted jobs elsewhere were hard to find and often of the lowest quality.
In a letter to the Guardian newspaper, the six charities said disabled people led more fulfilling lives in mainstream employment.
Jo Williams, chief executive of Mencap, said: "When the factories were started 60 years ago they were making an important contribution. Those days have gone really.
"We're looking forward to seeing people with disabilities fully integrated into society.
"Of course, for some people this will be difficult and quite frightening, I imagine, but they're not going to be abandoned."
Ministers say they want Remploy to take on more people, but without being given extra money.
Unions say this puts half of the factories and 2,500 jobs under threat.
Remploy chief executive Bob Warner said each job in its factories costs an average of £20,000, and for the same money four disabled people could be helped into other roles.
"There is now an acceptance that disabled people would prefer to work in mainstream employment alongside non-disabled people rather than in sheltered workshops from which they do not progress or develop," he said.
"I can give a guarantee that no disabled person will be made compulsorily redundant."
The GMB is launching a campaign to fight the closures ahead of a formal announcement by Remploy on Tuesday.