"Our analysis suggests that abstinence-only programmes that aim to prevent HIV are not effective," said Kristen Underhill, lead author of the study.

"This finding has key implications for policy and practice, especially in the US, where abstinence-only programmes receive both federal and state funding."

One such faith-based programme caused a recent stir in Britain, when a school was sued unsuccessfully by a pupil wanting to wear a silver ring as a symbol of her chastity -- violating uniform codes.

In general, such programmes have failed to become widespread in Britain -- possibly related to dwindling church attendance, as society grows ever more secular.

This contrasts with America, where one third of the President's anti-HIV budget is dedicated to abstinence-only programmes.

The findings of the study indicate that programmes emphasising the use of condoms are more successful at preventing HIV, as well as reducing unwanted pregnancies.

Some figures working in the field of sexual health believe that abstinence-based approaches could ultimately do more harm than good.

"There are even studies which show they can make things worse as people do not have the knowledge or confidence to have safe sex," said Ivan Blake of Brook Advisory Centres.