Since Christophe Decarnin took the helm at the fashion house Balmain, his sharp, sexy silhouette has become the most coveted – and copied – look around, says Harriet Walker

The fashion crowd are used to being ahead of the curve, but when in September last year Balmain's Christophe Decarnin sent models down the catwalk in frogged, shoulder-padded jackets, to a soundtrack of Thriller, no one could have guessed how perfectly – and poignantly – the designer would nail the upcoming zeitgeist of spring/summer 2009.

When Michael Jackson announced his tour, shortly before his death, wearing one of the label's black brocade versions – supposedly procured for him by French Vogue's fashion director Emanuelle Alt – inspiration and influence had come full circle. The Eighties trend was no passing fad; rather it was a full-throated revival and Balmain's shredded stonewash denim, Swarovski-coated mini-dresses and puffball skirts were right on the proverbial money.

And what a lot of money that is: with little from the collection selling for under £1,000, it is hard to believe that Decarnin's designs can have much relevance beyond the spheres of the very rich and the very, very rich. Yet, in the space of two seasons and having been at the helm of Balmain for just four years, he has become the most copied designer on the planet – and one more relevant to high street shoppers than any other. The label's unique selling point of tough, rock-chick nonchalance crossed with a Dynasty-style exuberance is not intellectual – no form-disguising, thought-provoking hessian sacks here, thank you very much – but it is intelligent, and it has invigorated the market from the very top (those who buy Balmain) and the very bottom (those who buy the myriad high street rehashes). It is wearable, it is sexy and it is recognisable: it's a marketing dream, known to many as 'Balmania'.

The French house was founded by Pierre Balmain in 1945 – at a time when Dior and Balenciaga were titans in a burgeoning haute couture market – and garnered a reputation in Hollywood for its sleek, ultra-feminine designs; Marlene Dietrich, Sophia Loren and Vivien Leigh were all loyal customers.

After the founder's death in 1982, Gilles Dufour, followed by Oscar de la Renta took over as designers of the couture line, continuing a reputation for functional modern design crossed with the best of old-fashioned European luxury: fur, sumptuous wool suiting and cocktail-hour glitz.

"Keep to the basic principles of fashion," Balmain once said, "and you will always be in harmony with the latest trends, without falling prey to them." That's all very well, but what about when your label becomes a trend in itself? There's a specific style at the moment, known as The French Vogue Look, which comprises skinny legs, sharp-shouldered blazers and teeteringly high, punky ankle boots, and is worn by the aforementioned Emanuelle Alt and her boss, French Vogue editor Carine Roitfeld. It's pure Balmain, and it's how most people in fashion right now dress or would like to dress; more and more it's how the high street windows are styled, and how the woman at the bus stop is dressed too. It is not often that one catwalk show spawns such a cohesive trend, nor are collections generally translated in such a wholesale commercial manner. But there is something about the Balmain aesthetic that makes people want to emulate it. And it isn't just the high-profile publicity from celebrities who wear the clothes, like Beyoncé, Rihanna and Victoria Beckham.

"What Christophe Decarnin has done to the house of Balmain is broken tradition," believes Kate Phelan, fashion director at British Vogue. "It's quite trashy, but it's glamorous, and there's a lack of that in fashion." Decarnin's powerful but glitzy look is regularly likened to that of Gianni Versace in his heyday; indeed, there has been little else as unapologetically glamorous, seductive or decadent of late, in an economic climate that induced many designers to fall back on sober and sensible staples. Before Decarnin, few would have thought that sequins were day wear, but for Balmain customers – few of whom, it's safe to assume, have a workwear agenda – why not dress down a sparkling miniskirt with clumpy boots and a blazer?

Equally important is the fact that these clothes can be incredibly flattering.

A feminine silhouette tapers from those infamous tennis-ball shoulders, which make waists look delicately nipped, and legs appear elongated. The silhouette is slim and dark, a triumph of modern body-con with none of those ubiquitous and attention-seeking soapstar bandage dresses. And where pieces are more outré – be they crystal-embellished mini-shifts with one asymmetrically tusked shoulder-plate, or fish-tailed floor-length gowns – the line and colour palette remain uncluttered.

So although the inspiration remains unequivocally Eighties, Decarnin makes good taste out of bad in a tough-but-chic way, perfect for any trendy, self-assured party girl.

After de la Renta's final couture season for Balmain in 2002, the label declined and eventually filed for bankruptcy but, with the upturn in the hyper-luxury market (and a climate that facilitated Burberry's £13,000 Warrior bag), investors took note of the cherished name, and Decarnin stepped in as creative director in 2005. The brand turned from a couture house to a ready-to-wear line, although its made-to-measure origins are still inherent in its astronomical price-tags, exclusive stockists and diminutive production runs.

Decarnin's first collection for the house, for spring 2007, was a hybrid of late Nineties influences (doubtless learned during his previous tenure at Paco Rabanne) such as chain detailing and sequinned snake yokes, and touches from the house's own archives – bell sleeves and over-sized cuffs that decorated silky mini-dresses and voluminous, glittered camouflage trousers.

It was a winning look, and one that launched Balmain back into the fashion consciousness, creating celebrity fuss and commercial furore. Decarnin had patented a glamorous grunge – known in the glossies as 'glunge' – that defined the twilight of the boom times before becoming a recession-defying luxury leader. It wasn't until autumn/winter 2008 though, that his eminence was fully established. The collection comprised the skinniest red leopard-print jeans and directional dhoti trousers, teamed with embellished jackets and sloppy vest tops, as well as glittery mini-dresses: all skin-tight, all unbelievably glamorous, but without looking too heavily produced. It was off-duty model style taken a step further – more models at play. The look here is from the autumn/winter 2009 collection, in which Decarnin's pop Eighties references solidified into a darker and more chic take on the most opulent of decades.

Now recognised as the brand that launched a thousand shoulder pads, Decarnin's mischievous and cartoonish take on the Eighties power essential is an idiosyncratic mix of the exaggerated shoulders first shown for spring/summer 2006 by Martin Margiela, and the heavily ironic retro shapes worn by hipsters in Williamsburg and Hoxton. This fusion of high fashion and street style is representative of the label's brilliantly successful melding of influences into something that is at once directional and wearable. It's also a quintessentially French girl-about-town look that appeals to the American – and mainstream – market by not being too buttoned-up or too conceptual.

Pierre Balmain's design ethic was timeless elegance; Decarnin's vision is something more timely. But it works: the brand's owner, Alain Hivelin, claims that sales have doubled since Decarnin joined. Projected sales for 2009 stand at £18m. They have also recently launched a footwear range designed by Giuseppe Zanotti, and began showing menswear collections again in January this year.

Still housed in the original atelier on rue François Premier, Balmain is the ultimate example of fashion's ability to reinvent itself. It's proof also that high-end glamour will never go out of style, regardless of how much it costs.