The first lady of style: Samantha's hot but is she worth it?

Norma Major would never have done it. Even brass-necked Cherie Blair may not have dared. But Samantha Cameron has now revealed herself as willing to use her fame as the wife of a party leader to sell actual goods. Retail, darling. Bags, to be precise, at £950 a time – and now marketed in a way that is clearly aiming to put her up among the new superstar stylists whose whims are driving sales.

"Sam Cam" has gone glam in pursuit of a place alongside the likes of celebrity bag lady Anya Hindmarch and even the new faces of Littlewoods, Trinny Woodall and Susannah Constantine. Until now she worked away quietly as the creative director of the stationer Smythson, trying to bring a little risky fashion sense to the previously fuddy-duddy company that makes notebooks for the Queen. She was happy to leave the limelight to her husband David while he worked his political booty to become the leader of the Conservative Party.

But now he's a political star who hangs out with Arnold Schwarzenegger, and Mrs Cameron has gone Hollywood too. Her latest creation – the elegant, expensive, quilted Nancy bag – was launched at a party at Smythson's new store in Beverly Hills, California, where the previously reticent designer was willing to be photographed alongside the stars. The effects of the pictures have been dramatic, with Smythson claiming to have sold out of the Nancy range quickly. (Only a few hundred were available, this being high fashion, but that amounts to nearly £300,000.)

The company has started comparing her to some of the biggest names in British style. "Samantha Cameron is doing just what other creative directors do for other brands," a spokesperson for Smythson told The Independent on Sunday yesterday. "People like Christopher Bayley at Burberry, Anya Hindmarch, Marc Jacobs at Louis Vuitton, Stella McCartney when she was at Chloé; the list goes on."

And so it does. Fashion is a lucrative market – we spend £39.2bn a year on clothes – but traditional designers are now having to fight for magazine spreads and sales with an increasing number of rivals, from television presenters who think they can make better dresses to stylists who are fed up with choosing frocks for the stars and want to be famous in their own right. And now politicians' wives.

"All and sundry seem to be jumping on the bandwagon," says David Hawkins, who studied at the London College of Fashion and has styled for James Morrison and Elton John. "I had formal training and I find it quite shocking the amount of people that don't know anything about basics, like pattern cutting and garment construction. These are basic tools. You wouldn't claim to be a mechanic unless you had studied mechanics."

Samantha Cameron does have credentials, though. She had a degree in fine art, a tattoo of a dolphin on her ankle and a strong sense of style when she joined Smythson in 1996. She is also the daughter of Lady Astor, an aristocrat who proved with her furniture company Oka that she knows how to choose and sell things.

And there is no doubt that even before she became the wife of the Leader of the Opposition, Mrs Cameron was the creative force behind the remarkable reinvention of Smythson, which has three royal warrants and provided black condolence books at the funeral of John F Kennedy.

Under her guidance it first tried a few modern twists on stationery before becoming confident enough to sell alligator-skin jewellery boxes and leather in shocking hues. Its most remarkable present is a £150 Bible in "bubblegum pink calfskin". This is not tacky, in the eyes of fashionistas, because the company has such a sober reputation. It is ironic and fun. Sales at Smythson rose almost as fast as David Cameron rose through the Tory party, and when the company was sold to financiers in 2005 she received – as a shareholder – a reported payment of £300,000.

Mrs Cameron did all this behind the scenes, mostly. But under the new owners, Smythson has attempted to take its profile up several levels, including breaking into the lucrative American luxury market. And has realised that one of its greatest assets is the well-bred, good-looking, slightly funky creative director who also happens to be married to potentially the next British prime minister.

Americans famously love the posh. In August Samantha Cameron appeared on the cover of Harper's Bazaar, along with two of her children. British handbag makers don't usually get that sort of attention, but there was nevertheless much mention of Smythson – and her list of fashion must-haves included a handbag, diary, silver pen, Bible and keyring all sold by the company.

Friends say Mrs Cameron is in danger of becoming the victim of a tactic that previously served her well. While David was rising fast, his wife buttressed her own identity as a creative woman by seldom giving interviews unless they were good for her company. That looked like discreet independence, then. If she carries on with the policy now, critics may well say it looks like Cherie Blair.

Mrs Blair stands accused by the Tory party of attempting to make big money from her husband's reputation while he was still serving the British people as a leader. Mrs Cameron does not, by instinct, like being the one under the hot lights. At the party conference in Blackpool, when her husband pulled her up on stage to share the applause for the note-free speech she had persuaded him to make, she looked deeply uncomfortable.

The lines between her professional and personal lives have become strangely blurred with the new bags too. They are called Nancy "to encapsulate timeless British style" said Mrs Cameron, "taking inspiration from characters such as the enigmatic and quirky Nancy Mitford and the stylish Nancy Lancaster". Nothing to do with her daughter being called Nancy then? Or Nancy Astor being a relative?

Smythson grew by 25 per cent in the last financial year, which coincided with the Camerons becoming more famous here and abroad, but the company insists it is not trading on them. "Prior to her husband becoming leader to the opposition, Smythson business was performing very well," said a spokesperson. "She is a working woman with a career in her own right and has been for a long time."

Samantha Cameron wanted to be in art or fashion when she was a student at Camberwell College of Art, then Bristol Polytechnic, where she partied with trustafarians and ravers including the trip-hop star Tricky. Smythson found a use for her unusual understanding of both modern culture and the tastes of its largely upper-class clientele.

Being creative director means having a say in colours, textures, papers and styles – knowing, for example, that a notebook called Snogs will appeal to the sort of girls who chase after Prince William. Does Samantha Cameron actually design anything? Yes, says the company. "She works up the initial sketches and is involved in every stage of the development from start to finish."

The design world is a crowded and bitchy place, with high rewards on offer. The amount the British spend on clothes has risen by 50 per cent in the past 10 years, influenced by the arrival of celebrity culture. "Celebrity stylists have a huge impact upon sales in the fashion industry," says Bryan Roberts, an analyst at Planet Retail. They do not just include designers any more but choosers, people whose reputations depend on their taste.

"The fashion world has totally expanded its boundaries," says Harriet Quick, fashion features editor at Vogue. "The old definition of who did what and where has completely broken down."

In America Phillip Bloch, who chose Halle Berry's Oscar acceptance gown, has become well known for his fashion advice; so has Patricia Field, who invented the Sex and the City style.

Katie Grand is creative director at Mulberry. "I really understand fashion and the history of fashion and craftsmanship," she says, "but there are certainly a lot of stylists who don't really know much about... much, really."

What they all have in common is the message: I am fashionable; I like this bag, therefore to be fashionable like me you should buy this bag. Now Samantha Cameron is being presented as one of them.

The irony is that she achieved remarkable success at Smythson before anyone tried to make her its public face – and if her husband were not leader of the Conservative Party, she might have received the credit that deserves.

Additional reporting by Toby Collins

Smythson

Samantha Cameron, 36

What was young tatooed art graduate Cameron doing at the stuffiest stationery company in the country in 1996? Starting work as creative director, and turning Smythson of Bond Street upside down. A friend of trip-hop star Tricky in Bristol, she knew pop culture but also spoke the language of the posh, who bought notebooks from Smythson. The Queen was a customer, as Winston Churchill had been. Sales soared when she introduced daring products such as a pink christening Bible and a journal called Snogs, made from the best (and costliest) paper and leather. Seen as the secret of the company's success she stayed on when it was sold in 2005. Now famous as wife of the leader of the Tory party, she has lately come out from behind the scenes to act as "ambassador" for Smythson as it enters the fashion market, leading to claims she is cashing in on her husband's fame. Recently launched £1,000 Nancy handbag at a star-studded party in Beverly Hills. The first batch sold out straight away

Littlewoods

Trinny Woodall, 42, and Susannah Constantine, 46

What do they know, this strident pair who bully the badly dressed on television? Enough to boost sales at Littlewoods by 30 per cent, and get themselves hired as the new faces of the store

Jigsaw

Kate Middleton, 25

Girlfriend of Prince William and new fashion icon, the elegant Kate could have ruled the world as a celebrity stylist. But she is reportedly leaving the retailer Jigsaw to work as a photographer instead

Mulberry

Katie Grand, 36

Proof that some journalists can do as well as criticise, she launched the highly influential 'Pop' magazine in 2000 but then crossed the catwalk. Has styled shows for Prada and Vuitton and is now the creative director for Mulberry

Sainsbury's

Anya Hindmarch, 38

The best bag lady of them all, she was Accessory Designer of the Year for the second year running at the 2007 Glamour Awards. Earlier this year, her £5 'I'm not a plastic bag' shopper caused supermarket riots and turned up on eBay for £175 JO