The GMB national college at Whalley Range, Manchester, is being put up for sale because the union says it cannot afford the pound;5 million needed for repair work.
The 50 staff have taken advice on a business plan to rescue it and have appealed for backing from patrons and the Labour movement.
Besides residential courses covering union education, the college, a grade II listed Victorian building, has a wider social role. It has trained volunteers for the Samaritans, staff from The Big Issue and provides teacher training for Manchester City education department. It also serves as a conference centre Staff hope it can survive. "When the GMB hit cash problems it decided that one saving had to be National College," said Dave Norton, leading the campaign to form a co-operative.
"But they have been working closely with us to find a way forward."
Mr Norton, who has been at the college for 17 years, said most staff were long-serving and spoke of a family atmosphere. He has been heartened by the support shown among the college's patrons at a public meeting held to discuss the crisis.
"In the first year we would look just to run as a venue - we don't have the skills to run courses. But we would want to develop thereafter," he said.
A GMB spokeswoman said that the building had been making losses every year.
"It is really expensive to run and the last time we had a storm the roof blew off," she said. "We will continue to provide education for our members and are looking at ways of doing that and at redeployment.
"While the decision has been made by the general council to sell, we will look at any proposal - the staff could purchase it as a co-operative."