Researchers from the Trust for the Study of Adolescence, based in Brighton, interviewed more than 3,000 teenagers aged 15 to 18 about their views on sex education.

The study, to be published next month in the journal Sex Education, revealed that most pupils want to learn about sex, relationships and sexual health at school. School was a more popular source of information than the internet, magazines, television or a partner. Only 40 per cent wanted to ask their friends for information about sex.

Sixty per cent wanted to learn about sexual behaviour, such as masturbation, and how to have satisfying sex. Fewer than 30 per cent were interested in sexual biology.

White boys were more keen than any other ethnic group to learn about masturbation and sexual technique but were the least interested in learning about emotions and relationships. Only a third of white boys wanted to know about contraception, compared with 55 per cent of Asian boys.

Lester Coleman, a co-author of the report, insists that this does not reflect a one-dimensional view of sex. “Some minority ethnic groups reported slightly poorer knowledge of diseases and contraception, compared with white young people,” he said. “So it’s about recognising gaps in their knowledge.”

Rebecca Findlay, of the Family Planning Association, said: “Young people are painfully aware that they’re not getting the information they need to navigate through a highly sexualised society.

“They want to talk about these things with their friends, but they need a certain level of information to be able to do that.”

* lcoleman@tsa.uk.com