The warning from Prospect – which represents 6,000 engineers, scientists and managers at Sellafield and the company’s 21 other sites – follows a spate of press reports that the Government is planning a sale of Westinghouse, BNFL’s American arm.

Prospect believes a decision by the board of BNFL is imminent, under pressure from the Government through the BNFL Shareholder Executive and the Treasury.

Dai Hudd, Prospect Assistant General Secretary, said any such decision would be "economic madness. It was this Labour Government which approved the company’s strategy to purchase Westinghouse. It clearly recognised its importance to the future of the industry in the UK, not to realise a quick buck like any market speculator. This is short-termism at its worst."

Westinghouse, which owns 70% of design licences for nuclear reactors worldwide and is the dominant player in the market for constructing nuclear power stations, would provide vital know-how for new nuclear build in the UK and enable BNFL to exploit the growing market for new build in China, the rest of Asia and the US.

It was bizarre, said Hudd, that just as nuclear power build was rising up the agenda as the answer to carbon emissions, the UK should seek to sell off its chief reservoir of new-build expertise to the Americans.

"The strategy the Government put in place in 1998 is coming to fruition as planned. This was confirmed by the BNFL Joint Strategy Review in 2003. Prospect has proposed that Westinghouse should be set up as a Public-Private Partnership. Any sale now will lead to its inevitable takeover by an American consortium and leave the British nuclear industry clinging to the coat-tails of the US, costing the UK billions of pounds in lost orders and ultimately jobs."

Mike Graham, Prospect National Secretary for the North West, said: "The sale of Westinghouse so early after BNFL’s restructuring in 2003-04 will destabilise the remaining BNFL businesses and associated employment. It will also cut off the 1,400 Westinghouse employees in the UK, engaged on fuel fabrication at BNFL Springfields, Lancashire, from the rest of the company.

"Prospect and professional staff at BNFL remain committed to a PPP model for Westinghouse. This would enable the UK to take advantage of the huge business potential for the company, while reducing the risk to the public sector balance sheet."