Women taking the combined oral contraceptive pill are at an increased risk of cervical cancer, according to the latest Oxford-based research.

But the risk starts falling soon after the pill is stopped, according to the Cancer Research UK study, which took place in Oxford. The study showed that 10 years after last using the pill, the extra cervical cancer risk disappeared.

The report, published in The Lancet, confirmed previous research linking the pill with an increased risk of cervical cancer, and revealed for the first time that the risk fell after pill use stops. Women currently using the pill, who have been using it for at least five years are at nearly twice the risk of cervical cancer, compared with women who have never used the pill.

Dr Jane Green, lead researcher based at Cancer Research UK's epidemiology unit at the University of Oxford, said: "This study confirms that women who are taking the pill have a small increased risk of cervical cancer.

"But this increased risk begins to drop soon after women stop taking the pill and after 10 years risk has returned to normal levels.

"The pill remains one of the most effective forms of contraception, and in the long-term the small increases in risk for cervical and breast cancers are outweighed by reduced risks for ovarian and womb cancer."

Cases of cervical cancer peak in woman in their 30s and there is only a small overall effect on the lifetime risk of developing cervical cancer from use of the pill by young women. Cervical cancer risk for women up to the age of 50 in developed countries such as the UK who have never used the pill is 3.8 in 1,000.

This increases to 4.0 per 1,000 in women who use the pill for five years, and to 4.5 per 1,000 for those who take the pill for 10 years.

Researchers looked at 24 separate studies of more than 52,000 women from 26 countries worldwide.

Dr Lesley Walker, Cancer Research UK's director of information, added: "Cervical cancer can be largely prevented by going for regular smear tests so it's vital that all women go for screening. In future, we hope that many more cases of cervical cancer will be prevented as a result of the recently-announced HPV vaccination programme."

Previous research has shown an increase in breast cancer risk, but a decrease in ovarian and womb cancer in women who take the pill.

The combined pill is the most common type of oral contraceptive and consists of two female hormones - oestrogen and progestagen.