John Urquhart, a researcher based in Newcastle-upon-Tyne in north eastern England, estimated that at least 200 more children than normal died during those three years.

"We've probably been too complacent about the health effects from Chernobyl in western Europe," he told New Scientist magazine yesterday.

Urquhart calculated that in England and Wales the fallout may have caused more than 600 extra cases of Down's Syndrome, spina bifida, cleft palate and other abnormalities in these years.

After studying deaths and birth defects in children born in 15 health regions of England and Wales between 1983 and 1992, he found that most of the increased deaths and deformities occurred in just five regions, spread throughout the two countries.

"Death rates fell every year except for 1986, with the extra deaths mostly occurring in four of the five same regions. The odds that the overlap occurred by chance are 1 in 200," according to the magazine.

Urquhart presented his findings to a conference on low-level radiation in Dublin.