Sellafield is the main asset of the newly-created British Nuclear Group

British Nuclear Fuels Limited (BNFL) said clean-up liabilities and costs associated with the plant's Mox fuel facility contributed to the loss.

Chief executive Michael Parker said the figure was "disappointing".

Earlier this year, the Cumbrian reprocessing plant was hived off by BNFL, with the creation of a new business called British Nuclear Group.

The company's loss before exceptionals compared with a deficit of �261m a year earlier.

Turnover, however, increased by 5% to �2.32bn.

Financial position

BNFL said more than �500m had been spent on discharging historic nuclear liabilities during the 12 months to 31 March, adding that its safety record during the year had been the best in its history.

Since the start of the new financial year, BNFL has put its clean-up activities into a separate company as it prepares for next year's creation of the Nuclear Decommissioning Authority (NDA), which will be based in Cumbria.

The NDA, a government body, will oversee the clean-up of nuclear sites in the UK.

Mr Parker said: "The loss sustained by the group in 2003/04 is disappointing, but the financial position will change dramatically once the NDA takes responsibility for a significant portion of our assets and liabilities as well as the legacy issues."

As part of the Energy Bill, which still needs parliamentary approval, the majority of BNFL's assets and liabilities will transfer to the NDA.

This will include responsibility for decommissioning plants at Sellafield, which state-owned BNFL has owned and operated for more than 30 years.