Depending on your taste in music, television-viewing habits and attitude to the raw mechanics of star-making, Simon Fuller is either the new messiah of pop or the Antichrist - a nightmarish reminder of the power of modern marketing. You may not care for the smiley charms of the Pop Idol gang, S Club 7 (now just plain S Club) or many of the other bantamweight performers he represents. You might not have forgiven him yet for the Spice Girls, whose ascendancy he plotted with such meticulous skill. You might even agree with Chris Martin, the singer with the hippest British rock band du jour, Coldplay, that Fuller should be 'melted down and turned into glue for destroying people's dreams and ripping them off'.

But never mind what you think; the chances are that at least one person in your family has bought into this 42-year-old Englishman's vision of how pop music should look and sound, and how it should be beamed into our lives. And if he maintains his momentum, that will soon apply to most of the families on Earth. When Fuller says, 'I'm very global,' he is not boasting.

From the vantage point of a rented mansion in Hollywood's swankiest quartier, Bel Air, Fuller is looking back on a phenomenally successful year. Although or perhaps because he is such an astute manipulator of media, he avoids personal contact with reporters, hates being photographed and has given scarcely any interviews since American Idol - the transatlantic version of the TV talent show he launched in the UK in 2000 - took the United States by storm. 'It's actually bigger here than it is in the UK,' he says, and again he isn't boasting.

By the time that American Idol's fresh-faced finalists, Kelly Clarkson, 20, and Justin Guarini, 23, were offered up to the popular vote this autumn, Fuller and his broadcast partners, the Fox network, were in possession of the highest-rating television show in the US, with an audience in excess of 20m, Fox's largest ever. The finalists, allof whom are contracted to Fuller's management company, are as big over there as Will Young, Gareth Gates and Darius are here. After the eventual winner, Clarkson, sang at a 9/11 memorial concert in New York, Fuller was invited to an after-show at the White House.

Since then, the victory parade has continued apace: Clarkson's first single entered the Billboard chart at No 1 in the first week of its release, the Idol finalists are touring arenas across the States, and such is the demand for more of the same that the second series of American Idol has already gone into production - well ahead of the next instalment of its British progenitor, which will not now hit our screens until next summer. By then, Fuller and his 19 Group of companies should have two more primetime shows up and running in the States with the CBS and NBC networks. When pushed, he reveals that one of them is a remake of the 1960s boy-band comedy The Monkees, which is being written by the team behind The Simpsons, and the other, more bizarrely, is a revival of the beauty pageant. Provisionally titled Superstar Girl, it aims to identify young women of exceptional, all-round talents. 'It's about intelligence, singing, dancing, general knowledge, swimming...'

Fuller is eloquent on why he spends so much of his time now dreaming up new ideas for television programmes - an unusual preoccupation for a pop manager who insists that music is his first love, that he is 'absolutely not motivated by money' and that 'the thing I still get most pleasure from is choosing songs for my artists'. Telly is an essential for a pop svengali nowadays, he believes, because the people who used to play a key supporting role in creating and sustaining the sort of stars he manages have fallen down on the job. At a time when British pop acts fail to penetrate North America, and news of declining music sales across the world prompts regular gloomy headlines in the business press, Fuller names the guilty men. 'Record company executives,' he sighs. 'Don't get me started. They're so lazy and spoilt. They're mainly interested in ego and money, and, worst of all, because they change jobs so often they have no loyalty to their artists. They've slowly been diminishing the value of artists for years by abusing their back catalogues, releasing endless compilations just to get the numbers to add up.'

And it gets worse. Years of what Fuller refers to as 'abysmal decision-making' has left the big labels hopelessly beholden to radio and TV companies who couldn't exist without their music and yet whose playlists they cannot control.

'And how abysmal is that? They've given away the crown jewels!' If he ran a record label, he says, he wouldn't allow radio the rights to broadcast any of his acts. Most of all, he is dismissive of the pop industry's indifference to what is truly popular. 'You shouldn't be arrogant about music. I've been dubious about A&R people for years, because I am one. For the most part, A&R guys are making records for themselves rather than the public, and when innovation does actually happen it has nothing to do with them. All my ideas are based on what I feel is a gap in the market. I might not like Steps, but I don't criticise 10-year-olds who love them.'

And he doesn't disparage the shopping malls or the TV ads, or the other unfashionable media outlets where these young - and not so young - people connect, however fleetingly, with the sounds they love. 'People listen to music in so many different ways now. You have to capture the hearts and minds of the nation by whatever means you can. You have to attack on all fronts.'

Despite the Hollywood pad and his two new offices in Los Angeles and New York, Fuller's empire is still based in Battersea, near Chelsea Bridge. Your first thought on visiting 19 Group is that it does not look like the hub of an international music and entertainment company whose turnover has quadrupled during the past 12 months and whose main proprietor was recently ranked in the top 20 of Britain's highest-earners in The Sunday Times Pay List. It sports no lights, no logos. A tight cluster of low-rise warehouse-like buildings behind wrought-iron gates, its most visible landmark is the smart riverside restaurant Ransome's Dock.But the bulk of the business transacted at Ransome's Dock Business Centre turns out to be being done by 19, and managing a couple of dozen pop acts is now only a part of it. There is the entertainment division, where ideas for TV shows and feature films are batted about; the S Club movie, out in spring, is a hot topic. Also in train is a version of Pop Idol for young Asian ladies called Pop Princess, principally aimed at the Chinese, while for everybody else on the planet there's an international variety show, The Biggest Show on Earth. This curious brew of animation, conjurors, circus acts and pop megastars such as Celine Dion and Britney Spears will, it is hoped, be fronted by local presenters in every territory where western entertainment holds sway.

And 19 is also home to a team of songwriters. One, Cathy Dennis, co-authored Kylie Minogue's monster comeback hit Can't Get You out of My Head. Others routinely supply the company's pop roster with material. Scarcely a week goes by without a song by one of 19's crafty tunesmiths featuring in the top 20. According to the music-biz online gossip site Popbitch, nearly a quarter of all music sales here this year have had some connection with 19.That's not to mention its other speciality, the sponsorship deals, such as the one that has tied S Club up with BT.

When he's in Britain, which isn't often at the moment, Fuller arrives at Ransome's Dock from his house in Richmond around 11am and stays, with maybe an excursion for dinner, until the early hours of the following morning. You could call him a workaholic but he says: 'I really love what I do.' And he does, a lot. During the course of the day he might talk marketing angles with Charles Garland, the man he poached last year from the ad agency Bartle Bogle Hegarty. He will almost certainly need a word with Nigel Lythgoe, formerly the controller of entertainment at LWT, now in charge of 19 TV and the person with hands-on responsibility for all things Idol.

Never far away is Catri Drummond, one of Fuller's longest-serving employees and a former girlfriend who has since assumed the role of his PA - though nobody at 19 describes her as such. On the two days a month when he isn't in Cornwall writing his novel, Richard Eyre, sometime head of ITV, Capital Radio and Pearson TV, is on hand to explore the sort of business partnerships that are needed to make some of Fuller's more expensive ideas happen. (Pop Idol started out as a joint venture with Fremantle Media.) For fun, he can always wander into his old friend Pete Evans's office and listen to some new tunes from his stable of songwriters.