Independent on Sunday, The: Hi, meet my new boyfriend. (What's his name again?)

Tussling for their man's affection 20 years ago, Elaine Paige and Barbara Dickson were both equally convinced that they knew him so well. It was probably true - back then, "having a relationship" meant some form of shared history, long-term commitment and the kind of insider knowledge that enabled a woman to list her partner's childhood scars in order of size and severity.

Nowadays relationships are formed in the queue for the supermarket car park, the first row blows up by the frozen peas, and it's time for the tear-stained parting of ways by the checkout. Three dates and you're having a "relationship" and if it falls apart the next day then this stranger becomes your "ex". And it very well might fall apart. Women in their twenties and thirties in particular are accelerating relationships like hydroponic seedlings; speeding up the natural growth process to the point where the entire fragile ecosystem collapses.

A survey commissioned by this month's Company magazine highlights what many single women of this age already know. Alarmingly, it showed that while 87 per cent of women insist that a new partner uses a condom, 25 per cent are happy to dispense with protection after a month, regardless of his sexual history, because by then, they "feel safe". At risk of sounding like Carrie Bradshaw: You trust him after four weeks? Why?

Some experts believe that sex itself is part of the problem. The first episode of Sex and the City, the series that gave us Carrie's wisdom, featured a debate on whether women could ever have commitment- free sex. Six years later, Rachel Morris, the psychotherapist specialising in relationship issues who fronts Channel 4's upcoming documentary series, Single Again, is still not sure that the answer is yes.

"For a lot of women, having an intense sexual relationship with someone is tantamount to knowing them intimately," she says. "In fact, they don't know him any better than anyone they've spent four hours in a pub with. But once we've slept with someone we like, we can quickly feel committed to them. And if you push a relationship at that pace, and emotionally cover six months of relationship in six weeks, you're going to burn out faster."

Back to Sex and the City - now drawing to a close - and the protagonists have all learned the advantages of committed love. But they're not prepared to hang around waiting for it, and neither, it seems, are we. The problem is not limited to women in their thirties nervously watching the clock. Lizzie Hosking, 23, a writer living in London, says she is looking for a committed relationship but her romantic CV is turbulent and littered with what many would call brief flings. She thinks of them as full-blown relationships, albeit fleeting. "I get really intense really quickly," she says. "I genuinely believe I've fallen in love and I think that can scare a lot of guys off. And if it doesn't, I find that after three months or so it's me who's lost interest."

Her mother (and experience) might tell her that you can't hurry love, but Lizzie isn't listening. She believes her fast-forward approach is due to thwarted expectations. "We are exposed to endless messages about what constitutes a good or bad relationship, we're financially independent and we have good friends whose opinions we can rely on. So if, after the first-month butterflies have gone something better comes along, we're not going to stick with what we've got." Despite this knowingness, however, Lizzie still thinks she's found The One every time. "I even know that the chemicals you get from sex at first are the ones that mimic falling in love, like dopamine - but I still keep mistaking it for the real thing, then being disappointed."

Impulsive Hollywood stars - Angelina Jolie and Jennifer Lopez spring to mind - marrying after a few dates and divorcing a couple of years later. Nor do stars with a relationship history like Geri Halliwell's, the ultimate speed dater. Geri has two famous "exes" perpetually linked to her name: Robbie Williams whom she was with for two months and Chris Evans, whom she dated for a reported 17 days four years ago.

We're all looking for love, but the more successful we are, it seems, the more we expect it to slot into our lives at our convenience. When we find something that resembles it, we lose all sense of proportion. So is the answer to become a Rules girl and hold out on the sex? Harley Street sexologist Dr Petruska Clarkson doesn't think so. "Sexuality is very important, and you don't want to waste time going out for dinner for weeks, then find out that the guy sucks in bed," she observes. "That's not the real problem anyway. The main problem is that our emotional expectations are so high nowadays, and men can seldom meet them all straight away. Women want men to be best friends, lovers, sensitive, successful and everything else so when they don't match up, they feel let down, even though he probably never offered that in the first place."

"Real relationships have down sides, they need to be worked at, yet we're constantly told that we can have perfection," says Rachel Morris. "It's fine to be ultra-choosy if you're younger and don't really want to settle down. but as the biological clock starts to tick, they may miss out on potential partners because they aren't prepared to compromise at all."

Women in their thirties who fast-forward their relationships, looking for "the father of my child" can discover, in fact, that they're not only fast-tracking would-be dads and finding them wanting, they're also exposing themselves to sexually transmitted diseases by playing Fertility Russian Roulette. "In the past, I sometimes didn't bother with condoms because I half-wanted to get pregnant," admits Annie Langley, 36, a freelance producer from Manchester. "I'd start relationships I hoped might turn into something special and part of me thought, `well, even if they don't, I could be a single mum'. STDs never occurred to me."

Annie was lucky - women in their thirties have one of the highest growth rates for HIV infection. "I was lucky I didn't get pregnant either. It was as if I was on a stopwatch. If he hadn't said he loved me by the fourth date, I used to feel upset. I'd ask leading questions, and refer to `us' and weave marriage into the conversation. No wonder it always ended after a few months - they were probably terrified."

She is now four months pregnant by her live-in boyfriend of two years, Peter, 38, a manager. "When I met Peter, we just got on so well, all that pushing and emotional testing wasn't relevant," she says. "We simply wanted to be together, and it was suddenly as if I could breathe a huge sigh of relief and think `actually, I'd enjoy taking the time to get to know you'. Before, I thought that by rushing things onwards, I could bypass all the things that weren't right. Now, I'm just glad none of them wanted to marry me in return."

Virginia Ironside, The Independent's agony aunt, thinks that to a certain extent you have to go with the flow. "This is the way relationships are now and most of us have to work within that," she says. "There are advantages as well - you could argue that if you take it slower you will just get more hurt when you do eventually break up."

The key, according to Rachel Morris, is self-knowledge, and a cool, realistic eye. She has been with her boyfriend, John, for 18 months: they moved in together after a week. The speed was, she thinks, "because I'm a romantic and an optimist, and so is he. But whereas in the past I would have rushed ahead, and then been devastated if it didn't work out, with John I accepted from the start that although it instinctively felt right, I couldn't assume it would never go wrong.

"There have been down times since, but crucially, when we met, we were both equally ready to commit to a real relationship, rather than a fantasy."

Because, of course, that's what the 0-60 relationship is. A fantasy of a true relationship based on intimacy, emotional openness and commitment - when all it's really based on is sex and hope. Who knows, you might be lucky, but if you keep your finger on fast- forward there's a good chance that you'll just to get to the end too quickly - and even worse, miss all the good bits along the way.