Celebrity perfumes are everywhere � but who wins the bottle royale?

As a child, I used to make perfume - a laborious and thankless task. Plump, pregnant roses would be stripped from neighbours' bushes and brought to my back garden. It never amounted to much: one or two drips of rose oil for every velvety bulb, for every cubic litre of sweat, for every drop of blood from the thorns. The memory floods back to me in the perfume section of a Glasgow department store, familiar, like the faces on the walls. Sarah Jessica Parker pouts on one advertising board; on another, a dripping wet Gwen Stefani leaps from the bottle of her latest fragrance. "Might be the sweat from crushing all those roses," I think, but probably not.

Celebrity fragrances form the fastest growing sector of the $2.9 billion (£1.42bn) perfume industry. Since 2004, their share of the market has soared by 2000%, and is now worth about £255 million in the UK alone. If the stats are to be believed, one in five of 16 to 24-year-olds regularly wears a celebrity scent. And there's ample choice. This year has seen more than 30 launches and the trend looks set to continue. "It is the year of the celebrity fragrance," says Julia Bolsom of The Perfume Shop. "We know our customers love celebrities and aspire to live a celebrity lifestyle It therefore follows that by spending a few pounds, our customers can feel that they are experiencing part of their favourite star's lifestyle." It's a statement that seems sublime and ridiculous in roughly equal measures. But the sales figures back it up.

Even if a perfume is not a celebrity fragrance per se, endorsement by a celeb is still important. Chanel No 5 is the world's most popular perfume: a bottle is sold every 30 seconds. In recent times, Nicole Kidman has become the face of the scent. "I'm a dancer," she announces in the label's plush Baz Luhrmann-directed commercial: "I love to dance." Keira Knightley struts for Coco Mademoiselle; Beyonce is the face of Emporio Armani Diamonds. Even smash-the-system artists like Prince are getting in on the act; his 3121 fragrance is the latest extension of his artistic (formerly known as commercial) vision.

Some have scrimped disappointingly on the aesthetics. Jennifer Lopez's Glow has a peach-coloured bottle that even my gran would balk at, a silvery plastic pendant that only the neediest of children could admire. Paris Hilton's Just Me spouts a toxic pink liquid, more toilet cleaner than eau de toilette. The bottle for Kylie's Sweet Darling looks like a bum. In some cases, the names, at least, are accurate. The commercial for Sean John's Unforgivable range shows the rap star in bed with two beautiful models which, sure enough, is hard to forgive. (The same could be said for the description of Sir Cliff Richard's Devil Woman scent, aimed at "Cliff fans and women who want a warm, musky fragrance"). Others contain various base notes of irony. The knickerless Britney claims to be In Control, while the loudmouthed Jade Goody has plumped for the incongruous Shhh.

For men, as with clothes, there is less variety. Pay your cash for a splash of Cumming, the new fragrance by Scots actor Alan Cumming; or try RSVP by Kenneth Cole, "inspired by the energy of rock legend Jon Bon Jovi". With top notes of grapefruit and wet grass, it's a favourite of my eager shop assistant, Gail.

"This one's magnetic," she tells me. "I have a friend who follows anyone around all day if they're wearing it." She sprays my wrist, against my better judgment. It might be my imagination, but the customers seem to part like waves. I get the feeling I could fill my pockets with goods, wrap myself in expensive jewellery, and the female security guard still wouldn't follow me out the door. Like those roses I once pulped, I'm trying to find the essence of the celebrity in their scent, mainly because I want to believe there's more at play here than cynical marketing. I inhale deeply from a tester strip and nearly keel over. "Benzophenone-3, butylphenyl methylpropional " says the back of the box. "No, no, no," says the front: "This is Intimately David Beckham."

George Dodd is a world-renowned perfumer and the founding father of the psychology of smell. Drawing on decades of experience, he creates personal perfumes at his Aroma Sciences studio in Wester Ross, based on a series of in-depth interviews with his clients. He has agreed to give me the lowdown on a selection, by no means complete, of the celebrity fragrance range. In turn, I have smuggled him as many free samples as I can carry: a whiff of Kate Moss in my pocket, a sachet of Paris Hilton in my hands; I've snatched the Beckhams (his and hers), a bottle of Covet by Sarah Jessica Parker, the scents of Kylie, Britney and several others.

I needn't have bothered with quite so many. "They're all very similar," says Dodd. "All very clichéd and innocuous. Around 80% of the formulation of modern fragrances comes from four incredibly cheap chemicals which are widely used in detergents. A woody note of some kind, synthetic musk, a balsamic note, a floral note ..." Of course, there are some distinguishing features: J-Lo goes heavy on the synthetic musk ("I don't know if you've ever got into a lift with an elderly lady ); Posh's fragrance is anything but ("There's nothing complex here, nothing sophisticated"); and Britney goes large on the fruit ("It actually makes my mouth water").

"It's important to refer to all of these as eau de toilettes and eau de parfums because none of them represents the true glory of perfumery," says Dodd. "If you go back thousands of years, the classic erotic ingredients have never changed - you're dealing with precious natural woods and animal musks." When his customers smell such concoctions, he says, their body language changes immediately. Their insecurities evaporate, and they walk around "in the wonderful atmosphere of their perfume".

It's an image reminiscent of Patrick Suskind's novel Perfume, in which the protagonist Grenouille concocts and wears a natural perfume so desirable that he is ripped to pieces by a frenzied mob. I suggest a similar fate would befall me if I were to buy a bottle of celeb-scent for anyone this Christmas. Dodd is more diplomatic. "All of these are fine for the price, like cheap plonk, but none has the animal vitality that you get in traditional French perfumes." By "animal", he means "the kind of feeling you get if you cuddle a warm furry creature - it's immensely erotic."

We can't blame the celebs for this lack of vitality. The main change came in the 1980s with the likes of Calvin Klein's Obsession range, which introduced what Dodd refers to as "linear design": a US philosophy of perfume, based on peppering low-cost synthetics with "a very light sprinkling of natural ingredients at the end". These days, the perfume world is dominated by six multinationals, which create simple eau de toilettes to cost, for celebrity endorsement or otherwise.

In turn, the higher-end designer label fragrances have been forced to economise with their products. Dodd estimates the manufacturing cost of most celebrity scents at just "a few pence" per 50ml bottle, despite retailing for anything between £15 and £40 in the shops. We pay instead for the packaging, and the all-important PR story. "People read articles about these fragrances in magazines that conjure up wonderful images of peasants collecting fields of rose petals and processing them," says Dodd. "But none of these have been near a flower in their lives."

He keeps returning to our sample strips, like a dog with a buried bone. Over time, the smells mature, revealing more of their composition. Kate, by Kate Moss, is "a little disappointing, a little abstract and ethereal," he says. "The entry note is what I would call edible berry, but it eventually ends up as a non-descript powdery note, which is common to all of the fragrances in this selection." He defines this powdery note as the "American theme", which is where the psychology of smell comes in. "American tastes are dominated by their perfume experiences when they're tiny babies, and get their bums powdered with Johnson's Baby Powder. All of these fragrances try to portray themselves as sexy but they're actually incredibly clean and innocent."

Less so the thinking behind the marketing, which at root involves a triangle, and the age-old law of aspiration. The theory suggests that if I admire someone famous, and that someone drinks Irn-Bru, then I, too, will choose Irn-Bru. But that model is being stretched. In the case of the new scent by Alex Curran, wife of Liverpool Football Club's Steven Gerrard, the variables multiply dangerously. Do I have to like her? Him? Liverpool? England? No matter: the fragrance is one of the top five sellers at The Perfume Shop, a few places behind Stunning, by Katie Price, and Sean John's Unforgivable, the expected Christmas number ones. Which suggests that shoppers have some strange aspirations.

"The smell is almost irrelevant as long as it's reasonably acceptable," says consumer psychologist Paul Barclay. "When you first drink beer, you don't like the flavour, but you learn to associate it with being part of the crowd. In most cases the people who think these fragrances are nice have learned to like them. The celebrity is simply used by the fragrance manufacturer as a shorthand for style and elegance."

Barclay thinks there may also be a "like-me" factor at work, where the everyday faces from reality shows have become our default celebrity noses. In what is being referred to as the Battle Of Big Brother, Jade Goody's Shhh now outsells Shilpa Shetty's fragrance S2, despite being hauled from shelves following the Channel 4 "race row" this year. The fall-out threw a spotlight on the risks of celebrity endorsement, where companies are just one tabloid backlash away from a warehouse full of worthless product. Slapping another big name on the bottle would be one way of clearing the backlog, and the chance is that nobody would notice. Dodd turns to David Beckham's Intimately Beckham, Night, and inhales.

"I would describe this as masculine and woody but the image of David Beckham certainly wouldn't come to mind," he says. "There's nothing unusual in the smell, but then apart from playing football I don't suppose there's anything particularly unusual about David Beckham."

We're running out of samples. I'm hoping Kylie's Sweet Darling fares better, if only because she's had a rough time of late. Nothing doing. "I've no idea what Kylie is like in real life," says Dodd, "but this fragrance certainly doesn't sparkle with the excitement I've seen in her dancing." The lid of the box opens like a coffin; Dodd hammers in the final nail. "We have to remember that these are mass-market products, tested on focus groups, and have to appeal to almost everyone in a target age range. Anything distinctive in the smell is going to be completely eliminated."

Back in Glasgow, my wrist is feeling less like Bon Jovi's by the second. For Christmas, Dodd has recommended Cabochard, which he describes as "the perfumer's perfume, and classically sexy". I ask Gail, my shop assistant, if she has any in stock. She doesn't, but wants to know who it's by. "Gres," I say. "No, Gris." The truth is I can't remember. I want to say Grace Kelly, Granny Smith, anything to latch on to a name. But Grace Kelly wouldn't make me any more glamorous, and Granny Smith wouldn't smell like real apples. I walk from the store, past Britney, dodging Kylie, with Dodd's words still ringing in my ears: "Do any of these fragrances evoke the personality of their celebrity? No, they very obviously don't."