Jemima Lewis: Sex, teenagers and the liberation of abstinence

I don't watch much television any more; it's all just chavs having sex with each other. But a few weeks ago, lying on the sofa, I channel-hopped on to something truly startling: a bunch of chavs not having sex at all. The BBC2 series No Sex Please, We're Teenagers, which finished this week, charted the progress of 12 teenagers who had pledged to give up nookie for five months.

Most of the teenagers, aged 15 to 17, had been at it like rabbits for years - though not always with much enthusiasm. Jenine, a mouthy rebel who became the show's star, admitted she had lost her jewel-above-price in a toilet, and didn't think sex was "all it was cracked up to be". Her dream, she confessed, was to "be in love with somebody and do it in a bed".

To help to make that dream a reality, she had enrolled at the Romance Academy: a scheme set up by two Christian youth workers heavily disguised as normal, funky twenty-somethings. Rachel - all skinny jeans and blond highlights - looked like a refugee from Atomic Kitten; Dan, in hip-hop sportswear and a blinging gold crucifix, gave the game away only when he referred to sex as "doing a whoopsy".

Rachel and Dan hoped to persuade their young disciples to "swap sex for old-fashioned courtship rituals". They took the teenagers to salsa-dancing lessons, gave them makeovers to show them how to dress with class, and flew them to Florida to meet members of the Silver Ring Thing, a Christian youth movement that preaches total abstinence before marriage.

American-style chastity didn't agree with our teenagers at all: they giggled through the touchy-feely meetings and baulked at the fundamentalist Bible-bashing. But celibacy itself, without the God element, seemed to do them a power of good.

Alone with the camera, each teenager confessed that he or she felt liberated by abstinence. All of them had come under intense pressure to have sex: the boys to show they were not "batty", the girls to prove they were not "frigid". Most had caved in - simply because, until they joined the Romance Academy, they could not think of a single reason to say no.

It's a chastening thought: we have created a society so liberal that it traps children into promiscuity. There is a lazy consensus in Britain that teenagers are bound to have sex anyway, so all we can do is try to make it safe for them. Although schools are supposed to teach "Sex and Relationships Education", the relationship part - and especially the part that involves waiting - tends to be rushed through en route to the more practical issues of condoms and morning-after pills.

Health workers, trained to be scrupulously non-judgemental in matters of jiggy-jiggy, bend over backwards to accommodate the contraceptive needs of children. At a conference in Belfast this week, Angela Star - recently crowned the 2005 Sexual Health Nurse of the Year - described how she had given a girl a contraceptive injection in the lavatory of a McDonald's.

Many teenagers, she explained, were reluctant to visit clinics so, instead, she goes to them. "I have been known to go to the school gates with a glass of water so I can give a girl emergency contraception," she declared.

I am not against plying teenagers with contraception; I just think it should be accompanied by a thorough talking-to. There is nothing wrong with telling teenagers that sex can be awful - and that the younger you do it, the more you are likely to regret it. If grown-ups won't tell them the truth, who will? I was lucky enough to be educated by nuns: world leaders in anti-sex propaganda. Our headmistress, Sister Caroline, was small and half-blind, but no less intimidating for that. She wore a severe black wimple and an enormous pair of spectacles. Her right eye was magnified to Cylcopean proportions, while the left was shrunk to the size of a raisin.

One afternoon, she summoned me to her office and, with a flourish like Hercule Poirot producing the murder weapon, laid a sheet of pills on the desk. "We found these contraceptive pills in your desk," she thundered. "What will your mother say?" Although I had nothing to fear - I was a virgin, and they were vitamins, and what was she doing rootling in my desk anyway? - the look of outrage in Sister Caroline's giant eye made quite an impression. I waited a long time after that to do my first whoopsy.

If modern teenagers are to be persuaded to wait, however, it cannot be left to Christians to cajole or intimidate them. There aren't enough Christians to go round. It is up to the rest of us, atheists and liberals, to help them to achieve that modest dream - of sex in a bed, with someone they love.