Scientists have identified a genetic factor that is linked with a 20% to 30% increased risk of developing bowel cancer. Although very rare genetic mutations have been associated with the disease previously, the newly identified mutation - which is carried by over half the general population - is the most common yet discovered.

Researchers do not yet know which gene or genes are affected, let alone how they might cause the disease, but they say the finding will help to intensify screening of people most at risk for the disease.

Bowel cancer is the second most common cancer in women and third most common in men with around 35,000 people diagnosed each year. Nine out of 10 cases occur in people over 50 and over the course of our lifetime each of us has a 5% risk of contracting the disease. "It is the most common non-avoidable cause of cancer death," said Ian Tomlinson, at Cancer Research UK's London Research Institute. The footballer Bobby Moore died of the disease and the charity set up by his widow Stephanie part-funded the research.

Professor Tomlinson's team identified the genetic link by collecting blood samples from around 1,000 people with a family history of bowel cancer who had developed the disease. They searched for mutations in their DNA that are more common than in a control group of people who did not have the disease. They found a mutation on chromosome 8 associated with the disease. The results are published in Nature Genetics.

Carrying the genetic variant raises the risk of the disease from around one in 20 to one in 16.