One in four smokers who carry a gene mutation will develop lung cancer, a large-scale study has shown.

The defective gene, known as BRCA2, has long been linked to breast and ovarian cancers. Scientists found that a specific flaw in the gene almost doubles the overall risk of lung cancer.

A quarter of smokers, who have a 13% risk of lung cancer, were predicted to develop the disease if they had the mutation.

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Study leader Professor Richard Houlston, of the Institute of Cancer Research in London, said: "Our results show that some smokers with BRCA2 mutations are at an enormous risk of lung cancer ... 25% over their lifetime."