The gene concerned, known as p53, normally defends the body against tumours. But its variant form, called p53Arg, is more easily blocked from working by the effects of HPV, the virus which doctors blame for almost all cervical cancers.

Britain's Imperial Cancer Research Fund said the work was carried out by researchers in Britain and Canada and published in the science journal Nature.

Dr Alan Storey, leader of the ICRF research team, said: "We found that cervical cancers resulting from HPV infection were significantly more likely to occur in women who had only p53Arg.

"This implies that p53Arg is a major risk factor for cervical cancer."

He added: "Testing for p53Arg may prove to be another useful tool in assessing a woman's risk for developing cervical cancer."

Skin cancer link

The findings also have implications for certain skin cancers linked to HPV infection.