It was not immediately clear whether skin samples only or limbs and tissues were taken for laboratory examination from the 1960s until the practice was stopped in the early 90s but there are suggestions that almost 70 bodies may have been affected.

Mindful of Liverpool's Alder Hey hospital scandal and other cases involving children's body parts being retained without consent for research, the government moved quickly to investigate the claims.

Alistair Darling, the trade and industry secretary, will make a Commons statement today promising to appoint a leading QC to establish the facts and issue a report. "The prime concern is the feelings of the families. There are clearly a number of matters that need investigating dating back to the 1960s," said the Department for Trade and Industry.

The GMB union went public with its call for an inquiry yesterday, four days after the area's two Labour MPs, Tony Cunningham and Jamie Reed, first heard the allegations and demanded an investigation from the chief executive of the Nuclear Decommissioning Authority (NDA), Ian Roxborough.

Between them the MPs represent most of the 13,000 staff at Sellafield, Britain's oldest nuclear facility. Mr Cunningham said last night: "This is very disturbing and we have already demanded a full and thorough investigation. The relatives have a right to know exactly what happened even many years ago."

What is suspected is that when an unusual death occurred at Sellafield, a heart attack in a young man for instance, a specialist doctor would examine the body and take samples of an unspecified character. It is claimed that other UK nuclear plants, Aldermaston and Harwell among them, were also involved in the procedure. But the doctor and two coroners said to have been used have died.

The issue came to light when a scientist sought to review the accumulated data to support new studies and asked how it had been obtained. "Grotesque as it sounds we do not know which body parts or where they ended up," said one MP involved.

British Nuclear Fuels Ltd (BNFL) said the tissue was "stored appropriately" until destroyed during research.

Stressing the issue was "historic not current", a BNFL spokesman said: "The sampling of autopsy material began in the 1960s and ceased in the early 1990s. Files exist at Sellafield for 65 cases. An examination of the data has shown that in 56 of those cases the sampling was done associated with coroners' post mortems or inquests.

"In five other cases it was done under instruction from other legally correct bases, such as family solicitors. For the remaining four cases there is no record of instruction or consent on file although this does not mean that appropriate requests were not made.

"The subject of sampling autopsy material came about now because of a request to re-examine the historic research data to support new studies.

"That request was made by the Westlakes Research Institute to the Westlakes/NDA Research Governance Group and this is being considered by that group, the company and the unions.

"Tissue samples waiting to be analysed were stored appropriately, on occasions for several months, however the samples were destroyed by the actual analysis process. There is no tissue stored on site today and the practice of taking samples for radiological analysis ceased in 1992."

The GMB's national officer, Gary Smith, said: "Our chief concern is for the families of those who died during this period and the anguish they face. We need information from the company and we expect a quick reply to clarify what has happened."