Roisin Murphy: Meet the poster girl of cutting-edge chic

When I meet the singer Roisin Murphy at a café after the House of Holland show at London Fashion Week, it's hard not to feel as comparatively uncool and drably dressed as a policeman at the Notting Hill carnival. She is wearing a pink and grey shard-patterned sweatshirt by Vivienne Westwood, and huge vintage Courrèges sunglasses, although this is actually quite a subtle look by her striking standards.

The catwalk shows might be where we get a glimpse of what le beau monde will be wearing next season, but the outfits people create to watch the shows have become as diverting as the collections themselves. This season, in New York, Paris, London and Milan, the former Moloko frontwoman-turned-solo artist was the one capturing style spotters' imaginations with a succession of looks that sealed her reputation as a fashion maverick, or as one impressed fashion blogger put it, "an arch kookster".

As buyers, journalists and celebrities spilled out of the London shows wearing various takes on the season's unofficial uniform of peg trousers, ankle boots and oversized blazers, Murphy always stood out. Her fashion-week ensembles included a cropped leather jacket with exaggerated, shaggy fur shoulders (made by one of Gareth Pugh's assistants, Gemma Slack), a cream draped dress by Topshop Unique and bowler hat by New York milliner Ellen Christine, a Charles Anastase sailor-style coat with Hermès beret and gold YSL postcard-effect bag, and a puffy red satin dress by Lanvin with Tudor shoulders and a feather headdress by Stephen Jones.

Outdone only by her friend Kabir, a stylist who memorably rocked a furry bear headdress at some of the shows, Murphy's approach to fashion is brave and experimental; the opposite of just picking up on the season's trends. Later on in the evening, after we meet, she models in Naomi Campbell's Fashion For Relief charity show, strutting down the catwalk in a Westwood outfit alongside Vivienne and her husband Andreas Kronthaler. The designer rang Murphy after meeting her at a party, to which the 35-year-old singer wore a "fabulous green taffeta Westwood gown, mixed with a Calvin Klein bomber jacket", and asked her to appear. "She has the softest hands I've ever shaken," says Murphy, her Irish accent muffled by very un-fashion week mouthfuls of pasta and tomato sauce.

Murphy's whirlwind, one-woman-fashion-week round of the shows is also "window shopping", for her current tour, which began yesterday and will include the Brixton Academy. She is famed for her adventurous stage and video outfits, and says, "I have the wardrobe on stage with me and I change for almost every song." Inspiration for recent live outfits came from a Martin Margiela ensemble she wore with a Philip Treacy hat in the video for "Let Me Know", from her second album, Overpowered, in which she dances around a diner.

Murphy explains, "It consists of a sheer white body suit and a skirt that becomes a cape at the back. It has big white pointy shoulders," she adds, "and they became a bit of a thing with me. The main element I loved was the body suit, which I wear with a pair of trousers on stage and it creates a kind of modular system which hats, coats, shoulder pieces, gloves etc can be layered on top of. It's a very ingenious idea even if I do say so myself!" Murphy adds that her stage outfits are essential to her performance, "not to hide behind, but to say something about the song, and to express more intensity through the music. There's also a lot of narrative in the songs, sometimes it's literal – in "Checking Up On Me" I look over my glasses and strike a rock and roll pose – and sometimes it's more abstract.

"For me to go on stage just wearing jeans and a T-shirt would be dishonest. It would be like me saying, 'Oh I'm just like everybody else, you don't have to be scared of me.' I think that for everyone who loves what I do there are people who are intimidated by it." Certainly outfits such as the Gareth Pugh ridged white dress (think Stormtrooper meets armadillo) she wore to the shows in Paris, shortly after it had appeared on the catwalk, are exhilaratingly unusual rather than conventionally flattering. Even aged nine she had an exhibitionist streak, as demonstrated by the time she "went up to town and got my long blonde hair shaved into a marine cut". When she came home her dad started crying, but she "loved it – it was liberating".

Murphy attributes her love of clothes to her mum, whom she describes as a natural clothes horse. People in Dublin would approach her mum and ask for her autograph, mistaking her for Faye Dunaway (Murphy also bears a notable resemblance). The pair would go charity shopping together in posh areas of Manchester, where her family moved from Ireland when she was 12, and would snap up vintage Jaeger. She says, "If you can't afford designer labels, go to a charity shop and buy an old T-shirt because they only start to look good after 10 years. The whole thing of going to a high-street chain and buying a T-shirt in every colour just in case you might need it is incredibly wasteful. I think that idea has been forced down our throats a bit."

Away from fashion week and on the tour bus, doesn't Murphy ever feel the urge to sneakily pull on a tracksuit? It seems not. "I have two Margaret Howell plaid shirt dresses, they're my nighties," she says, "and I have Margiela mock cropped boots, they're my slippers. And I put my YSL mac on and that's my dressing gown. And if I'm really feeling rough I put sunglasses on as well. I have to think in terms of there might be fans waiting and I don't want to let them down." The sight of Murphy emerging from the tour bus in such an unremittingly stylish take on leisurewear is unlikely to disappoint.