Health chiefs are urging schoolgirls to take up a vaccination against a sexually transmitted disease that causes cancer.

All girls aged 12 and 13 will be offered free vaccinations against the human papilloma virus (HPV), which causes 99 per cent of invasive cervical cancers.

The move is part of a nationwide campaign which will immunise around 300,000 girls.

Cervical cancer, which affects the neck of the womb, is the second most common cancer among women under 35 and kills around 1,100 every year.

The immunisation programme comes after health minister Dawn Primarolo announced that the new Cervarix vaccine could save 400 lives a year.

All 17 to 18-year-old girls will also be offered a routine vaccination from next month in the hope that by 2010 all girls leaving school will be protected against cervical cancer.

Barbara Hamill, immunisation coordinator for Barnet Primary Care Trust (PCT), said: “Our priority is to protect girls in their early teens, and I would urge all in these age groups to have the full course of vaccinations to help protect against cervical cancer.”

Letters will be sent to the parents of all schoolgirls in the age group through their schools. The PCT needs parental consent to give the 12 and 13-year-olds the injections, but is aiming for an uptake of 90 per cent.

Dr Andrew Burnett, medical director of Barnet PCT, said the combination of vaccinations and cervical screening, which can detect the cancer at a very early stage, will have a major impact on incidences of the disease.

He added: “We now have a condition which is avoidable in young adults. The fact that you can immunise against it means people can protect their children against the cancer as well as the diseases that cause it.

“My hope is that parents will discuss this with their daughters and encourage them to have it.”

The vaccination protects against two strains of HPV which are responsible for around 70 per cent of cervical cancers.

The programme has provoked some controversy over concerns that immunising 12-year-old girls against sexually transmitted diseases could encourage underage sex. But the vaccine is more effective if administered before girls become sexually active.

Dr Burnett added: “I wouldn’t expect a 12-year-old girl to be sexually active, but this prevents a risk that they will in all probability be exposed to in the future.

“You might say it’s like shutting the stable door before the horse has bolted.”

Cervarix was chosen by the Government over another vaccine, Gardasil, which also protects against genital warts — an STD which is rising steeply among young people.

In July it emerged that the choice of Cervarix over Gardasil would save up to £18.6 million, but some sexual health campaigners criticised the Government for missing the opportunity to provide wider protection for girls.