Michael Meacher, the former environment minister, has called for an official investigation into a nuclear fuel factory which has so far cost taxpayers more than £600 million.

The factory, run by BNFL, was approved in 2001 by the prime minister, who overruled critics from inside and outside government who said that it would be a financial disaster.

The factory, at Sellafield in Cumbria, produces nuclear fuel derived from plutonium and uranium from BNFL's reprocessing operations.