The risk to workers at nuclear plants has been under-estimated because scientists have used the wrong measures, it is claimed.

Researchers say a reliance on studies into survivors of the A-bombs dropped on Japan at the end of the Second World War do not give an accurate picture of the effect on nuclear power workers.

Scientists from the University of North Carolina claim radiation safety levels are set too low and would be higher if other studies were taken into account.

But the National Radiological Protection Board (NRPB) in the UK disputed the claims that only A-bomb studies were used when setting radiation safety standards.

Dr Steven Wing, at the university's school of public health, said there was an "outdated emphasis" on A-bomb survivors.

He called for lessons learnt from nuclear workers to be taken more seriously and claimed people were being exposed to greater cancer risks than was generally accepted.

'Undue influence'

Military and industrial interests had an undue influence on research, he said, and it was difficult to obtain data and funding to carry out studies.

He said in scientific journal New Solutions: "As researchers and policy-makers come to appreciate the unique advantages of studies of nuclear workers, these studies should make a greater impact on occupational and environmental exposure standards."

But the NRPB said a range of studies, including those carried out on A-bomb survivors, nuclear workers and people affected by the Chernobyl nuclear accident, were all taken into account by international committees setting radiation exposure standards.

And the board challenged the idea that standards would be set at different levels if studies of nuclear workers were given precedence.

A spokeswoman said: "Estimates of radiation exposure are made on the basis of the totality of relevant knowledge and should not rely on individual studies.

"However, large studies of UK nuclear workers give risks that are consistent with other data."