Remploy is set to argue that it wants to place more disabled people into mainstream employment rather than in sheltered workshops.

But unions representing the 5,000 disabled staff who work in Remploy's 83 factories across the UK will call for the sites to remain open.

A document, said to be an internal memo listing 22 factories earmarked for closure, which was sent to the GMB was described as a forgery by the company.

The memo was said to be from Remploy executive Jill Hill to another executive, John Waterhouse.

Bob Warner, Remploy chief executive said: "The letter being circulated by the union is a forgery. No such letter was written either by Jill Hill or by anyone on her behalf and it does not stand up to even the most cursory examination."

Unions have criticised six disability charities who wrote a letter last weekend in support of the closure plans.

Mencap, Mind, Radar, Scope, Leonard Cheshire and the Royal National Institute of Deaf People said disabled people are more likely to have fulfilling lives by working in "the inclusive environment which the rest of us take for granted".

The GMB reacted with anger to the letter and warned of an industrial dispute which could break out just as Gordon Brown takes over as Prime Minister.

Remploy's management will meet union leaders in London today to outline plans which the company said are aimed at expanding the number of jobs it finds for disabled people.