Scientists have raised a new safety fear over the Sellafield nuclear plant by suggesting that the children of past employees at the installation were twice as likely to develop blood and lymph cancers.
In a large-scale study, cancer researchers at the University of Newcastle monitored the fate of nearly 10,000 children fathered by men who had worked and had been exposed to radiation at Sellafield.
It contrasted them with more than 250,000 children born between 1950 and 1991 to other fathers in the county of Cumbria, in the UK, where the plant is located.
Incidence of leukaemia and lymph cancer was twice as high among Sellafield children compared to Cumbria as a whole, the researchers found.
The incidence was 15 times as great in Seascale, a small village next to the power plant.
Crucially, the risk to children rose in line with the radiation dose received by their fathers.
Population mixing was suspected of contributing to most of the extra risk in Seascale.
But this could not explain the two-fold increase in risk among children throughout the county.
The researchers stressed the risks were small.
Only 13 children of Sellafield workers had contracted leukaemia over the past 41 years. Workers now received much lower doses than they used to.
Details of the study, which was published in the International Journal of Cancer, are carried in the latest edition of New Scientist.
It has reopened speculation as to whether a number of children of employees at the Sellafield plant had contracted cancer due to radiation exposure to their fathers.
Research 12 years ago first suggested such a link. However, those findings were criticised in some quarters as unreliable, because many people moved in and out of the Sellafield area and could theoretically have spread infections which could increase the cancer risk.
The latest research was part-funded by the Westlakes Research Institute, which is sponsored by Sellafield operators British Nuclear Fuels.
BNFL's health director Mr Paul Thomas said: "This study is very reassuring for our workforce and confirms that the excess risk of leukaemia and non-Hodgkin's lymphoma, particularly in Seascale, can be largely attributed to population mixing."
But a spokesperson for the anti-nuclear group Cumbrians Opposed to a Radioactive Environment said the study vindicated the earlier research on the issue, "and it is irresponsible for BNFL to ignore it".