Delaying cervical cancer smear tests until women reach the age of 25 is putting younger people at risk, a new report claims.
Researchers said rates of CIN3, which is the most significant type of cell change that can lead to cervical cancer, are increasing among women aged between 20 and 24.
Figures from the Office for National Statistics (ONS) show 3,000 to 4,000 women in this age group in England will have CIN3 every year.
But guidance introduced in 2004 excludes them from the national screening programme.
Dr Amanda Herbert and colleagues, from NHS trusts across London, examined national rates for invasive cervical cancer and CIN3.
Writing in the Journal of Family Planning and Reproductive Health Care, they said failing to invite young women for screening "may mean that a few will enter the programme 'too late' to avert cervical cancer".
They added: "Rates have been consistently higher in women in their 20s and 30s compared with later decades of life.
"Since 1989, rates have increased in women aged 20 to 24 and 25 to 29 years, while decreasing in those aged 35 to 39 years and above.
"The increase in younger women has taken place against a background of falling screening coverage since 1995, which has been most pronounced in women aged 20 to 24 years."