Changing sexual habits may be to blame for a sharp rise in cervical cancer in young women, experts said yesterday.

The incidence of the disease has risen by more than 40 per cent among women in their 20s in the last two decades, although the number of cases is still low. But in older women, in whom the disease is more common, it has declined, leading to an overall fall in the cancer of 30 per cent.

The reason is thought to be that women have sex earlier and have more partners. Most cases of cervical cancer are linked to Human Papilloma Virus (HPV) which is a sexually transmitted infection. In older women the rise is being curbed – and reversed – thanks to cervical screening, which detects changes in the cervix before they develop into cancer. In women in their 20s, screening is less effective because the cervix is changing naturally and signs of cancer are harder to detect.

The age for the start of screening was raised from 20 to 25 in 2003 because it was picking up "abnormalities" that were normal changes, and causing more harm than good.

The figures were released by Cancer Research UK, which funded the study in the British Journal of Cancer. They show the incidence among 20 to 29-year-olds rose from 5.5 women per 100,000 in 1992-94 (around 215 cases a year) to 7.9 per 100,000 in 2006-08 (283 cases a year) – a rise of 43 per cent.

The latest figures for 2007-08 suggest that the rise in incidence is continuing, with a rate of around 9 per 100,000 for women aged 20-29.