The contraceptive pill protects women against some cancers for more than 35 years after they stop taking it, the longest study ever carried out into the health risks has found.

In recent years there have been fears that the combined pill raises cancer risk, but new research by the University of Aberdeen found that, for ovarian, endometrial and bowel cancer it actually has a strong preventative effect.

Although there was a slight increase in risk for breast and cervical cancer, the study showed it was only a temporary rise and the danger vanished a few years after stopping contraception.

The Oral Contraception Study was established by the Royal College of General Practitioners in 1968, seven years after the pill was first introduced into Britain on the NHS. It has followed 46,000 women ever since to monitor the long-term impact.

It found that taking the pill for any length of time lowered the cases of bowel cancer by 19 per cent, endometrial cancer by 34 per cent and ovarian cancer by 33 per cent.