The shirt off his back

Fashion's hottest new look needn't cost a thing. Raid your man's wardrobe, advises Jess Cartner-Morley

The best thing to steal from boys, as every girl knows, is pudding. Why put yourself through all that calorie angst when you can casually push the dessert menu aside, in manner of thin girl who prefers olives, and still stuff your face with a generous half portion of tiramisu?

Now, this what's-yours-is-mine-sweetie attitude could be the key to a whole new wardrobe. Girls have always borrowed their boyfriend's clothes - and from F Scott Fitzgerald belles borrowing tuxes from their beaux to Kate Moss in a giant parka, it has always looked cool. For next season, the "boyfriend's jacket" look has blossomed into a genuine catwalk trend. A key silhouette in Stella McCartney's autumn collection is "an oversized coat thrown over a dress, as if casually borrowed from a boyfriend"; and at Chloé, Phoebe Philo explained that her jackets were "oversized, like your boyfriend's".

Always quick off the mark when there are new outfits at stake, fashion industry girls are already getting in on the act. Sara Forage is 23, and an account manager at fashion PR agency Purple. Despite an impressive wardrobe of her own, she has no qualms about pilfering from the wardrobe of her style journalist boyfriend Jonathan Heaf. "I think a girl looks really cool in her boyfriend's clothes," she says. "I saw a picture of Sofia Coppola wearing a man's jacket and shirt - so they were loose, rather than fitted - with skinny jeans, and she looked amazing. The kind of clothes that look best on a woman are a man's shirt or blazer, worn with a miniskirt and little trainers. There's something a bit sexier about being covered up: it says a lot about a woman's confidence that she doesn't feel she always has to show off her body."

Stylist Allegra Roberts, 28, has found her wardrobe possibilities vastly expanded since moving in with her fiance. "As I'm always telling him, his clothes look much better on me. Especially his tweed jacket. I force him to let me wear it by going on about how charmingly feminine I look in it."

Designer Katie Hillier, 27, also pleads guilty to a little "borrowing". "When baggy jeans were in, I used to wear my boyfriend's really expensive Levi's, the kind you can only get in Japan - they look great on girls because they sit really low on your waist. Unfortunately he caught me one day and wasn't too pleased. Boys' belts look great on girls, too, especially Hermès leather ones tied in a knot. But then, of course, you do get in trouble for tying them in a knot."

The most covetable men's clothes are the most masculine, as these have the most impact when worn by a woman. One of Hillier's favourite looks is "a girl in a Crombie with a man's scarf - that looks great." Old-fashioned coats, blazers, shirts and ties look good because the precise tailoring offsets the outsized effect, so the silhouette still looks sharp. Loose jeans and giant parkas, meanwhile, have a certain boyish swagger.

Even boxer shorts, it seems, aren't safe. Hillier recommends "boxer shorts on the beach, with a bikini top, surfer-style" while Roberts borrows a pair for sunbathing in the garden. "I wear them with a strappy vest. I'm convinced they make my legs look thinner." Dedicated followers of fashion also brave the prospect of skeletons in the closet, pillaging the depths of men's wardrobes for more outré fashion items. One brave girl was delighted to find a boilersuit - a discovery that might have horrified less fashion-forward girlfriends - and now wears it with stilettos.

But it's not just an insatiable appetite for new togs that motivates us ladies to dip into men's wardrobes. Even fashionistas have feelings, and there is a strong emotional draw to the sensation of wearing your loved one's clothes. Men's clothes always seem to smell faintly of their owners - we'll draw a veil over what this says about their laundry habits - and the best kind, it is universally agreed, are the well-worn pieces they've had for years. I have to hold my hands up on this one: my husband's sweatshirts are the next best thing to a cuddle, as far as I'm concerned, and several of them spend a lot more time on me than him. However, I always return them to his wardrobe - partly for appearances' sake, but mainly because there's no room in mine.

Men's clothes are also, of course, extremely comfortable. There are times when even the best-dressed women really cannot be bothered to squeeze themselves into their Seven jeans and skinny jackets. My sister Alice prefers to raid her boyfriend's wardrobe on a Sunday, "when all my clothes look too complicated to negotiate with a hangover".

Do men mind? After all, for most couples, body shape dictates that this is a one-way arrangement. And if they started helping themselves to our hundred-quid Crème de la Mer moisturiser, we'd be screaming blue murder.

Polly Hudson, 27, a news reporter for Heat magazine, is a fan of her boyfriend's jeans. "It's easy to get going-out jeans for girls, but it's hard to find nice, relaxed, slouchy ones, so I wear Bryan's. He doesn't really mind, but he did get cross the time I cut off the waistband - they were his favourite pair, and they had a zip so they just fell apart."

Hillier loved wearing her boyfriend's Turnbull & Asser pyjamas, but took the hint when he bought her a pair of her own for Christmas.

Roberts prefers a more assertive approach. "I don't borrow his clothes so much as blatantly steal them. Once I have worn them, I claim them as mine. I mark them by spraying them with my perfume, so he can't wear them." In fact, she has sometimes kept the clothes longer than she has kept the boyfriend. "My boyfriend at university had a blue cord Levi's shirt that looked great with jeans, and I wore it for the duration of our relationship. When we split up, it was the only thing we fought about. I won, naturally. It's still in my wardrobe."

There appears to be no end to pilferers' motives. One jacket-borrower, who preferred to remain anonymous, likes the suggestiveness of wearing her man's clothes. "It looks like you've just had sex, you see." With so many reasons to steal, it seems this petty crime epidemic is about to explode. Men, you have been warned: lock up your jackets.

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