So, after eight years out of power, the Tories have finally come up with their grand plan for tackling the problems of teenage pregnancy, binge drinking and drug use - they're going to tell young people to "just say no". Shadow Health Secretary Andrew Lansley said rising rates of binge drinking and sexually transmitted infections among young people were caused by "low self-esteem and peer pressure", and pledged an agenda to reverse this moral decline.

Anyone over the age of 30 will remember the menacing icebergs that became the iconic images of the Conservative government's HIV campaigns in the 1980s. While it is true that the campaign raised public awareness of the issue, many people now have doubts about the wisdom of employing such fear tactics. Tom Yocum, of the Terrence Higgins Trust, says: "One of the problems with the campaign was that it exaggerated the risk so much. People thought there was going to be this huge epidemic. When that didn't happen, I think it started a situation where people like heterosexual men thought they were immune and didn't need to practise safe sex, and that has led to the complacency and the rising rates of infections that we have today. Most people working in the field of health promotion agree that fear tactics do not work."

As with other issues, the Conservatives seem to be flirting with health policies that have been enthusiastically adopted by George W Bush in America. Abstinence campaigns, where teenagers pledge to stay virgins until their wedding day, are held up as an example that Britain would do well to adopt.

Andrew Lansley's themes of self-esteem and peer pressure are cornerstones of American abstinence projects such as the Silver Ring Thing, which encourages teenagers to don a ring that symbolises their commitment to chastity before marriage. But the most recent research on abstinence campaigns has shown that while they may delay the age at which participants have sex (at most by 18 months), more than 80 per cent of them break the pledge within a few years. More worryingly, projects such as the Silver Ring Thing tend to mislead youngsters about safe sex, telling them that condoms don't work, the Pill is dangerous, and implying that sexually transmitted infections are fatal.

In a study by Columbia University, teenagers who had taken a virginity pledge were a third less likely to use any kind of contraceptive when they first had sex than youngsters who were not involved in abstinence projects.

Under Labour, the Teenage Pregnancy Strategy has made slow but sure reductions in conceptions among girls under 19. It has taken brave steps, such as giving the morning-after pill to under 16s, and encouraging frank discussions in schools. And the fact is that these are working in a way that abstinence campaigns never have.