Victoria Beckham eats a grape, swallows demurely and explains the public relations strategy behind her new single. "If you don't like it, don't buy it. And if you don't like me, don't read about me. And if you think I look like an old bag, don't put a picture of me in the paper. I'm not that desperate to be liked."

We're sitting in a sunny conservatory of the Spice Girls office, just off the Edgware Road in London. Around the walls there are large photographs of the Spice Girls performing in concert. There's Sporty, Scary, Baby and of course Posh, in that pouting, thunderstruck pose that she deploys in most of her publicity pictures.

But where is Ginger? Above the door a photograph has been turned upside down, the subject's legs now waving in the air. Geri Halliwell may not have been airbrushed out of the Spice Girls' history like a pop cultural Leon Trotsky but she has been made to look ridiculous.

Posh Spice slices a peach into bite-sized chunks and calls for a Diet Coke. She's wearing a tight white top with a little matching cardie, pink jeans, open-toed shoes and a lot of make-up. She is carrying a handbag decorated with feathers of which she is inordinately proud. All these clothes and accessories may well make profound designer-label statements, but I am ill-qualified to make judgments about such matters. She looks healthy - by no means as thin as, say, she looked in those pictures that led the Mirror to proclaim her as an anorexic on their front page. Across the table, Dane Bowers, with whom she has collaborated on her new single, puts the lid on a Tupperware box that contained his healthy seafood salad. Posh eats another grape and he sips on his mineral water. For crying out loud. What happened to the rock'n'roll lifestyle, to brain-cell destroying benders, illicit hallucinogens, trashing hotel rooms and a different groupie every night? It rushed past this place at top speed: here, instead, the talk is of how essential it is to live right, eat well, and the importance of ab crunches to the modern figure.

Victoria Beckham defends the family and monogamy, champions the work ethic, and speaks of showing the way to ambitious youngsters. She's no Keith Moon. "I think I'm a pretty positive role model for kids. I'm not out getting pissed every night, shagging loads of different men, and if they slag me off at the end of the day, then I don't really give a shit." Why, say the eyes of PR woman lounging on a distant sofa, must Victoria be so foul-mouthed, so defiantly garrulous in interviews?

Why? Because Victoria Beckham knows this game better than most. She may be only 25, but she brings to her relationship with the media both a shamelessness and cunning that often wrongfoot PR people and journalists. Who else, after all, would have the gall not only to present a TV show in which she defended her celebrity and those of her friends, but to use it to interview her husband, the Manchester United footballer David Beckham?

That said, for a while now Victoria Beckham, née Adams, has been famous for little more than being famous. She has become the apogee of the modern British celebrity: she is everywhere all the time but her presence often begs the question: what exactly is she famous for? Her singing career has seemingly been eclipsed by something much more forceful, namely her hunger for fame and her thick-skinned ability to deal with its downside. When OK! magazine devoted two issues to her wedding last year, it became disturbingly apparent how far she was prepared to go to bask in the public eye. As one flipped page after page of Posh and Becks posed in various colour-coded wedding outfits, it was hard not to reflect on how much time the couple had given over to having their pictures taken, and how little they had spent out of the frame.

It couldn't carry on like that. Sometime, surely, she would have to step beyond the camera, come back from holidaying in St Tropez, step down from the catwalk and put little Brooklyn (now 16 months old) in a crèche while she made her next career move. She would have to follow the other Spice Girls into a solo career. After all, Mel C has put out an album, Scary has produced some R&B work, Geri Halliwell has made a solo career of some note - why, even Baby Spice had done something or other. Creative silence alone spoke loudly from Posh Spice's corner.

Why has it taken her so long to make a record? "It does hit hard if you're being told every day you can't sing, you can't dance. And that's what I was being told by the media on a daily basis. I'd had enough of it really. It was David who built up my confidence. I spent a long time thinking about what I would do next. I think the reason this new record is so polished is that we went into the studio with strong ideas."

It's a musical career that will be hard to ignore over the next year. After the single, which is A-listed on Radio 1, whose video is ubiquitous on MTV, will come a Spice Girls seasonal campaign to dominate Christmas. "We've recorded an album with a double-A-side single coming out in October - Let Love Lead the Way and Holler. We did it with Rodney Jerkins. He's the bollocks at the moment." [Jerkins is a voguish producer currently working on Michael Jackson's new album.] And in the spring, Victoria Beckham's solo album will be released.

She is working hard, she reckons, and is enjoying it. "I live off stress. I love it. It's like an adrenalin thing. I've got so much respect for women out there who are working mums. Even when we were recording I had a crèche for Brooklyn in the studio." The new single shows her media cunning once more. Thus, Music Week eulogised: "Who would have thought that Posh Spice would re-emerge as the most credible of the Spices? Although not as immediate as Buggin' [Dane Bowers and the Truesteppers' recent hit single], the Truesteppers' second release is a sure shot contender for the top of the charts. This is a triumphant release."

But why is it the most credible? Victoria Beckham has chosen to work with happening DJs on a garage track - the cutting-edge sound of Britain in the first summer of the new millennium. This may be a track with a hook strong enough to topple Robbie Williams from the number one single slot next week, but it also has enough cachet to make Posh seem hip.

Does she expect the record to go to number one next week? "I don't know. As far as we're concerned it's already a success." Interesting - the record isn't released until Monday.

But there is a tension here in Posh Spice's career. It may be necessary now and again for her to make a record, but, really, will Victoria Beckham ever be taken seriously as a musical artist? Arguably, the Spice Girls are less important as singers and dancers and more important as icons of a can-do, highly sexualised feminism, one that both proselytised in favour of autonomy for young women, and paradoxically promoted a rather conservative moral agenda - respect for one's mother loomed large, as did fidelity, personal ambition and the superiority of friendship with other girls to fickle male lovers. They couldn't sing (much), they didn't look (particularly) wonderful, but none of that mattered: they were recognisable as young women you might sit next to on the bus. And it was these personae, these mix-and-match social and political views, that caught a mood and made them exceptionally interesting. The music was only significant in that it gave expression to Girl Power and showed their astuteness at manipulating the pop world and the media. Admittedly, the Spice Girls may have been invented on the back of an envelope by some bloke, but let's not spoil the story.

The critic Gilbert Adair recently distinguished between art and culture. Art was the film, the song, the book; culture the talk about the work of art. In the modern age, art had become less important than culture. In fact, you needn't experience the former to talk satisfyingly about the latter. Something rather similar is happening to our most interesting celebrities. Yes, they may have to put out a record now and again, write a book or stage an exhibition, but that is hardly what makes them compelling. The single, the book, the film, is a pretext for a much more creative work of art - the artist's performance of his or herself.

This is a degraded, decadent age of Tracey Emins and Spice Girls; perhaps it is one that must be overthrown by another artistic revolution; it is clearly one that privileges exhibitionists and neurotics rather than those who have particular geniuses in making music, poems, paintings or films, but it is not, nonetheless, wholly contemptible or alienating. In this society of the spectacle, the best we can hope for is that the spectacle will be engaging. And so far, against all the odds, Victoria Beckham has managed just that.

In this sense, her self-confessed mediocrity doesn't matter much. "I'm not the best singer or the best dancer in the world, but I work hard," she says. "And that's what I'd want to say to kids out there that if you want something enough you can do it. I was picked on a lot at school. I was never particularly good at anything at school but I had a lot of drive and ambition. I didn't even have a nickname because nobody would talk to me. I think that's what makes me a good role model."

In a pop world dominated by young women singers such as Britney Spears, Mandy Moore and Christina Aguilera, who are perhaps not always aware of how they are being constructed as sexual objects for more or less perverted men, Victoria Beckham and the rest of the Spice Girls are a much more subversive proposition. For what the Spice Girls have insisted on throughout and what Posh Spice expresses nearly every time she opens her mouth is that they are not objects but subjects of desire. They are knowing enough about the media whirl to use their exposure to proclaim themselves as strong women rather than patsies created for male delectation.

Thus, when Victoria Beckham spoke, as she did at the weekend, of her desire for a new baby and mused that it was likely one would come along soon because "David is an animal in bed", apart from the vulgarity of this display of conjugal sexuality, something more interesting was afoot. Women, especially British women, weren't supposed to talk like that in public.

"Yes, I said that," she admits, grinning. "He is." She doesn't say what kind of animal, but my money is on a squirrel. Don't get your nutcases over the clean duvet cover, babe. "Some woman in an interview the other day said are you so thin because you shag all day? And I said 'Actually yes. And I bet you would too if you was married to David Beckham. And she's gotta say 'Yeah, I would!'" Sometimes this reflex aggressiveness can seem tawdry, as when she takes on those people who have criticised her appearance in print. "You get these people in the newspapers, right, and there's always a little picture of them. They are so bloody ugly it's like what a surprise that you work for a newspaper and you're not on telly."

This initially sounds catty, but it is not: after all, if someone does criticise your appearance incessantly, then why should there be an obligation to be aloof and not respond to those criticisms? "You can't let it get to you [people judging you for your appearance every day]. I know I'm a minger. [An ugly person. She's being ironic.] There's always this stuff about my weight - one minute they're saying she looks too thin and another minute she's really looking good and healthy and yet I'm weighing exactly the same and I'm wearing exactly the same clothes. It all depends on how people want you to look."

But is this constant scrutiny of her and her husband's lives tolerable? How can she deal with fame when it entails such vileness as the abuse the couple suffered during the Euro 2000 tournament when David Beckham left the field after a match against Portugal to the chant: "Your wife's a whore, and we hope your kid dies of cancer." "They'd been shouting those things at him for the last two years. It's only now that people are picking up on it. I think it's just that Kevin Keegan is such a supportive manager that he actually stuck up for David and said to the media 'I heard what they were saying'. If it hadn't been for him saying that then they would have done what they do usually which is to say 'Oh it's his temperament', or 'He's got a bad temper'. You get Roy Hattersley saying 'It's part of his job. He can't react like that'. It's not part of his job to take all that abuse! I just think he [Hattersley] is a misinformed has-been and that's being polite about the guy.

"David does take a severe amount of people slagging him off. Do they do that for Ronaldo in Italy? I don't think so. They put him up on a pedestal and they say 'Good bloke. You're talented, you're working hard.' And then if he ever does decide to go, it'll be 'Oh, why's he going?' And it's like 'Why do you think?'"

These are the kinds of incidents that would make a more private person go and live in Kazakhstan and live a life of silent contemplation, but not Victoria Beckham. Rather, she is looking forward to being even more exposed as her solo career takes off. "It is more risky. That's part of the attraction. You really get to shine in your area. It's taken me so long to pluck up the courage to actually do something. And it took a lot of encouragement from David saying 'God you can do this. You can write good songs'. That actually got up my confidence.

"When I went in and started recording demos I surprised myself and I thought: 'Yeah, you can actually do this.' And I can."