Sleeping with numerous women protects a man from prostate cancer, a study has found.

Research showed that Lotharios with a lot of notches on their beds are significantly less likely to develop the disease.

Compared with men who have had only one sexual partner during their lifetime, those with a score of more than 20 conquests have a 28 per cent reduced risk of being diagnosed.

The findings are from the Prostate Cancer and Environment Study in which 3,208 men answered questions about their lifestyle and sex lives.

Lead researcher Professor Marie-Elise Parent, from the University of Montreal, said: "It is possible that having many female sexual partners results in a higher frequency of ejaculations, whose protective effect against prostate cancer has been previously observed in cohort studies."

The study found that men who were virgins were almost twice as likely to be diagnosed with prostate cancer as those who were sexually experienced.

Compared with those who had had only one partner, men who had slept with more than 20 women were 28 per cent less at risk of prostate cancer of all types.

They were also 19 per cent less likely to develop an aggressive type of cancer.