Their union, Prospect, spoke out on 30 September after reports that the BNFL board had decided to recommend the sale of its operating arm BNG to the BNFL shareholder executive and the Department of Trade and Industry.

Mike Graham, Prospect National Secretary for the North-West, said: "This is a huge step coming just two days after the Prime Minister told the Labour conference that the country would have to look again at nuclear power to meet our emissions targets.

"The UK government must retain responsibility for the nuclear industry in the UK. BNG must not be sold off to the highest bidder but to the most competent. This is the most safety-critical industry in the UK. There cannot be a Hatfield at Sellafield."

Prospect wants the Department of Trade and Industry to spell out open and transparent criteria for conducting any sale and for strict adherence to technical, safety, environmental, trading and employment standards.

"These criteria will be all the more important if there is to be a sale to a foreign consortium as is all too likely," said Graham. Overseas buyers are already queuing up to buy Westinghouse, BNFL’s US operating arm, which the board put up for sale in July.

Graham is writing to Alan Johnson, Trade and Industry Secretary, seeking assurances over the terms of the sale, which is estimated to be worth up to £150m to the government. He expressed particular concern at the impact of selling BNG on the industry’s ability to deliver new build, just as the Nuclear Decommissioning Authority is launching a high-speed programme to decommission the ageing Magnox reactors.

Over 15,000 workers would transfer to a new employer if BNG is sold, including 6,000 scientists and engineers represented by Prospect. They work at the Sellafield reprocessing plant in Cumbria, and at 18 nuclear sites around the country. Prospect is also seeking assurances over the pay and conditions of staff and full protection for the company’s pension fund.