It said that it is believed that one of the four chosen bidders will be Barclays Private Capital, alongside another private equity bidder and two trade bidders.

On the eve of an expected announcement, Prospect national secretary Mike Graham said: "When BNFL announced the sale of its specialist decommissioning business in March this year, it pledged that its key objective was to ensure the delivery of value to the shareholder, along with a good home for its people and the safe and expeditious delivery of contracts to its customers.

"These were the words of chief executive Mike Parker. Prospect fears that a private equity owner would pose a threat to members’ job security and create a brain drain to other industries, which the decommissioning industry can ill afford.

"Project Services has already lost out in the bid for the Drigg low level waste repository and failed to win an expected contract at Dounreay. Surely this is not the time to be looking for a private equity owner, given the crisis in the money markets and the potential difficulties such a company may have in raising money, whether to run or invest in the business.

"This will send out all the wrong messages to staff, many of whom will feel compelled to leave rather then remain in a risky environment. At a time when skill retention is a major issue, this is something the government and employers cannot ignore."

Prospect has 15,000 members in the nuclear industry. Project Services employs over 730 highly skilled experts – most of them Prospect members – with extensive technical waste and decommissioning expertise in the nuclear and hazardous waste industries.

It holds contracts on nuclear sites, including Sellafield and Magnox reactor sites, and is involved in work for the Ministry of Defence, BERR, and the Home Office. A large growth area for its business is the emerging nuclear clean-up market in Central and Eastern Europe.