Two separate studies published in a leading medical journal have shown sex education does not reduce the number of teenage pregnancies or increase contraceptive use.

Canadian research found programmes failed to delay intercourse, improve birth control use or cut the number of pregnancies.

And a Scottish study of school-based sex education found that while it improved the quality of young people's relationships and their sexual health knowledge, it had no effect on their use of contraceptives.

This research confirms that sex and relationships education is just one important element amongst many in reducing teenage pregnancy

Anne Weyman Family Planning Association

But the Family Planning Association said the studies showed sex education was only one factor in reducing teenage pregnancies and successful initiatives took a much broader approach.

The Canadian study reviewed 31 trials of teenagers aged 11 to 18 which evaluated sex education classes, abstinence programmes, family planning clinics and community programmes.

In five of the trials examined - four abstinence programmes and one school-based sex education programme - an increase in pregnancies among the partners of young men involved was observed.

The authors, from McMaster University in Hamilton, Ontaria, Canada, say the review shows there is not yet a clear solution for reducing pregnancy rates.

Writing in the BMJ, they suggest sex education may need to begin when children are as young as five.

They add that the social reasons for teenage pregnancy need to be further investigated, adolescents need to be involved in designing sex education programmes and countries such as the Netherlands, which have low rates, should be studied.

Improved knowledge

The Scottish study compared the specially designed sex education programme called SHARE, aimed at 13 to 15 year-olds, with conventional sex education.

It involved 25 secondary schools and 5,854 pupils who were questioned before and after the scheme.

Teenagers preferred the SHARE scheme. Those who were on the programme had fewer regrets about first intercourse with their most recent partner and said their sexual health knowledge had improved.

But there was no difference between the SHARE group and those receiving conventional sex education in terms of sexual activity or contraception use by age 16.

It would be dangerous to conclude that sex education is useless

Dr Daniel Wight Glasgow University

Dr Daniel Wight of the Medical Research Council's Social and Public Health Sciences Unit at Glasgow University, who led the research, said: "One of the things that surprised us most about the study was that the majority of those who were having sex were using contraception and condoms responsibly.

"That might well be as a result of conventional sex education.

"What the study proved was that its very difficult to change the behaviour of the minority.

"It would be dangerous to conclude that sex education is useless, rather, that you might have reached as far as you can get with this sort of sex education."

He said methods where people can access sex education advice when they need it, rather than in set lessons at a set time in the school year could help.

Tailor education

Anne Weyman, Family Planning Association, said: "This research confirms that sex and relationships education is just one important element amongst many in reducing teenage pregnancy.

"Social exclusion, poverty, low educational attainment and access to services are also key factors in this complex public health issue.

"No one type of intervention can be successful alone."

She added: "The government's teenage pregnancy strategy is built on the 'multi-faceted approach' recommended in the research.

"Early outcomes are encouraging, with a fall in the conception rates of under 18s of over 6% since 1998.

"High quality sex and relationships education, begun early, tailored to young people's needs, linked to sexual health services and well delivered by trained staff remains of vital importance in enabling young people to make informed choices about their sexual health."