An official inquiry is to be launched into claims nuclear workers who died in the 1960s and 1970s had body parts removed without consent.
Tests were carried out between the 1960s and 1990s, said BNFL
The GMB union says samples were taken from up to 70 former employees at Sellafield in Cumbria.
British Nuclear Group, which owns Sellafield, confirmed autopsy material had been used for "legally correct" purposes such as inquests.
Trade secretary Alistair Darling will make a statement to MPs at 1240BST.
He is expected to appoint a lawyer to lead an independent investigation into the claims.
The GMB claims workers' body parts were removed for medical examination without the knowledge of families.
These included tissue, bones and body parts removed without permission, it is claimed.
GMB 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."
A spokesman for the Department of Trade and Industry said: "The prime concern is the feelings of the families.
"There are clearly a number of matters that need investigating dating back to the 1960s."
Prospect, which represents workers at Sellafield, also called for a public inquiry after claiming that from the early 1960s until the early 1990s vital organs were removed from the bodies of former workers who had died from cancer.
The union said organs were removed from more than 60 workers at several BNFL sites, as well as workers at the Atomic Weapons Establishment at Aldermaston.
In a letter to BNFL it said the only way to counter concerns was for the company to clarify its policies and actions at an independent public inquiry.
General secretary Paul Noon said: "We don't want to rush to judgment but we do want the facts.
"Removal of organs from deceased radiation workers without consent would be ethically, morally and possibly legally wrong. Whatever the motives it should not have happened."
A spokesman for BNFL said: "This is an historic issue not a current one, however our prime concern is the feelings of the families of those involved.
"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."
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