Only Happy When It Rains, Queer, Subhuman. And those are just the titles of Garbage's harrowing songs. Caroline Sullivan on a band with a troubled singer obsessed with depression and self-destruction

Ever wondered why the Brit Award for best female artist always goes to some pleasant dullard (Gabrielle, Eddi Reader and this year's winner, Shola Ama, spring to mind) who barely impinges on our consciousness the other 364 days of the year? It's because only women who've had hit (Top 75) albums are eligible, and the list of those is pitifully short. Last year there were just 12, excluding all-girl covens like All Saints and the Spices, and including Shirley Bassey, Sarah Brightman and violinist Vanessa-Mae.

To put it another way, there are hardly any commercially successful British female singers, and of those, even fewer deviate from the norm. Other than witch-woman Polly Harvey and folk weirdlet Beth Orton, there's... well... not many others... To this minuscule roll it's time we added, in the shiny black letters she favours, the name Shirley Manson.

Edinburgh-bred Manson has a solid advantage over the others. As vocalist/lyricist with the Wisconsin-based rock quartet Garbage, she's sold four million copies of the 1995 album Garbage, which was nominated for seven major music awards. Their second LP, Version 2.0 (out later this month), is widely expected to repeat the success of the first. It might be more romantic if she were a marginal cult figure, but her success is heartening, proving there's room at the top for an original mind and brimming bagful of neuroses. In America, the group's biggest 'territory', she's an alternative icon second only to Courtney Love.

'I get a lot of women fans and a lot of incarcerated men,' she reveals, sitting motionless as a make-up artist reinforces a thick layer of silver glitter on her eyelids. 'I get odd things in the post. Someone sent me a pair of Vivienne Westwood boots with no note. No idea who they were from.' Did you wear them? 'No.' Back in 1984, there was a hit by the band Was (Not Was) with a chorus she might appreciate: 'Woodwork creaks, and out come the freaks'. The woodwork has creaked, and the 'freaks' are clustering, drawn by Manson's marble-cool languor and songs whose bleakness is easily inferred: Only Happy When It Rains, Queer, Subhuman. Shirley receives fan letters claiming eternal devotion on the basis of lyrics like: 'I'm only happy when it rains/My only comfort is the night gone black/I'm riding high upon a deep depression'. Someone even sent her an animated video of herself as a super-heroine - in which, presumably, she vanquishes baddies who make life hard for misfits and square pegs like herself.

Most female artists try to deter potentially obsessive fans, but she empathises with them, perfectly convinced she's the most freakish of them all. Manson believes - not in a wow-I'm-so-crazy sense, but profoundly - that there's a gap between her and the rest of the world that fame has only widened. Her life is ruled by the conviction that she's grotesquely unattractive, which is aggravated by spells of depression that have plagued her all her life. Nothing will change her opinion of her looks, not photographic evidence, fan mail nor four million record sales. 'There are moments of despair when you are absolutely an island and can only rely on yourself,' she admits.

There's a posh name for Manson's problem, Body Dysmorphic Disorder, colloquially known as Imagined Ugliness Syndrome. 'It's a recognised disorder,' confirms the Institute of Psychiatry's Dr Raj Persaud. 'It's when people believe there's something desperately wrong with some part of their body when they actually look normal to everybody else.' In her worst photos, Manson looks merely tired and thin, wide-set eyes dominating a wan face. At her best, as here in this London photo studio, she's a beauty. Her red hair ('Red hair really does shape your life in untold ways - for years I found it revolting'), creamy skin and translucent green eyes would be striking even if she didn't have the delicate bone structure to match.

But Manson looks in the mirror and sees 'a bloodhound, a fish, with big, baggy eyes. That's what people used to say to me. I was told I was ugly from the time I started secondary school, and I still see everything people used to freak out about. 'Oh, you look like a bloodhound... ' Her voice still curdles with hatred for her tormentors.

So you honestly can't see how pretty you are? Her lip curls in a dainty sneer. You've got a beautiful mouth, I say desperately, strangely set on cheering her up. 'That's what my mother used to say,' she replies, sighing, 'I have a lot of trouble at photo sessions and videos.' So would anyone who thought they resembled a dog. Manson's lack of self-esteem, made more acute by her crackling intelligence, trickles into her songs like a poisonous drip-feed. The first album burns with her masochism. 'Pour your misery down on me,' suggests the typically Mansonesque Only Happy When It Rains.

The excellent Version 2.0 is less anguished, perhaps because she recently married her boyfriend of seven years, but is still not exactly Spiceworld. 'Somebody get me out of here, I'm tearing at myself/Nobody gives a damn about me or anybody else,' drawls the languidly seductive Medication, while You Look So Fine sums her up concisely: 'I'm not like all the other girls/ I can't take it like the other girls'.

'I err toward despondency,' she says, her beautifully-rounded vowels a testament to her working-class father, who brought her up to be an omnivorous reader. 'It probably has to do with being Scottish, too, because the literature is steeped in tragedy and murder and disloyalty. Happiness is not a normal state of being - it's a gift, not your God-given right.' Which was why, for the inside cover of the debut album, Shirley chose a pose that reflected her own state of being - eyes huge, mouth stretched wide with her fingers, The Scream brought to life.

Arrayed behind her in the photo, the Garbagemen - drummer/effects-monger Brian Vig and guitarists Duke Erikson and Steve Marker - are also making faces, but their best efforts don't make them look like anything but the farm-bred Midwesterners they are. They're simply not screwed-up enough at heart.

That said, we can extrapolate major screwed-upness from Vig's CV. The producer of Nirvana's groundbreaking album Nevermind, the amiable 38-year-old must harbour a well of psychic despair to have been able to communicate with Kurt Cobain. But in interview mode there's no sign of it. He joshes with Marker, 37, and Erikson, 46 (Garbage have been around the block a few times - Shirley is the youngest at 30), with a wryness incompatible with Nirvana's angst. But for their indie-rock goatees, they could be any of the checked shirts that populate Madison, Wisconsin, the centre of America's dairy industry.

We're in London, but as Vig (shortened from Vigerson by his Norwegian-immigrant grandfather), Erikson and Marker shoot the breeze it feels like an unheated enclave of Madison. How did these boys next door end up in a group with someone as intense as Manson? 'There's a dark underbelly to our bright and cheery facades,' Erikson claims, hurt.

'We have a collective sensibility, because Madison is on the same latitude as Edinburgh,' adds Vig, not altogether convincingly, with a proprietary stroke of his piratical beard. 'We like songs with shiny pop melodies and really dark lyrics, and each listen reveals new layers of darkness. Dark songs make me feel better than happy songs. Happy ones I turn off.' Erikson is equally keen to impress. 'We're right in the epicentre of depravity. Ed Gein (a notorious serial killer) came from an hour north of us, and Jeffrey Dahmer was an hour south.' So there.

By an odd coincidence, the three. who'd been working as highly-paid producers/remixers for artists like the Smashing Pumpkins and U2, met Manson the day Cobain was found dead of a self-inflicted gunshot wound. The suicide had no bearing on the decision to form a band, which had been made earlier. Shopping for a singer, the three Americans saw a video of Manson singing with no-hoper Scots band Angelfish, and went to London to meet her - on April 8, 1994, as Cobain's body was being discovered in Seattle. It's apt that a band whose business is, as Manson puts it, 'the intense and the perverse, obsession, perversion, self-destruction, hedonism, faith and the lack of it' formed on such a day.

Garbage, the album, was a very nineties confection of synths, guitar-noise and gleaming melodies, all enrobing the dark heart of Manson's lyrics. There's a morbid fascination to it, 'like bad drugs', as someone has said - all those layers of voluptuous melody conspire with Manson's deceptively languid vocals to drag you down to some unnameable scary place. And all from three anonymous backroom boys and a woman who was too self-conscious to go shopping alone till she was 28.

Vig's heavyweight credentials got the new group its first flurry of attention, but Manson quickly emerged as the focal point. A string of hit singles such as Only Happy, Supervixen and Stupid Girl were very much products of Manson's battle with herself. 'I've never been to therapy, and don't have a lot of truck with it, but my American friends say I'm just the sort of person who should go to therapy,' she says in the same cool way she addresses all topics. It's hard to imagine her letting go to the point of crying onstage, as she did in New York at the end of an exhausting tour. 'I'm a flaming mass of contradictions, but why should I want to fix that? People should just live.'

One would hate to be the object of the pitiless scrutiny to which she subjects herself and most other things. She possesses an intolerance for foolishness that must make her a formidable adversary. 'I loathe jokes,' she says when asked if she knows any. 'Hearing them just fills me with disgust. Though I do confess to being amused by The Fast Show.' Although the singer has spent much of the last four years in Madison, where she resides in a hotel ('too frightened' to live alone in an apartment), she's still

Scots to the point of flying home specially to vote in the devolution referendum.

But absence from Britain has helped crystallise what it is she hates about the place.

'British sandwiches represent everything that's wrong with this country. Little anally retentive things with the crust off and a limp slice of ham. We don't like to be comfortable. In the States it's not considered a sin to indulge yourself.' Not that she ever would, of course. Manson's eco-system depends on continuous discomfort, a trait she shares with every truly interesting pop woman from Patti Smith on. It can't be easy being her, but her pain is our gain.

Version 2.0 is released on May 11