'If you step outside the mainstream you gain this great strength.' Singer-songwriter Roisin Murphy on the Mercury Prize, Moloko and being an outsider

It's fair to say that for most of us, Murphy remains the voice of Moloko, the dance duo she formed with her one-time partner Mark Brydon in the early 1990s. In its lifetime, Moloko morphed from the itchy electronica of Fun For Me to dance anthems like Sing It Back and the blissed-out Balearic beats of The Time Is Now.

But that was then. For most of the 21st century, Murphy has followed her own idiosyncratic path, one that has seen her work with producer (with a side order of mad scientist) Matthew Herbert sampling brass mice and cosmetics for her debut solo album Ruby Blue, become matey with Gucci's creative director Frida Giannini, and even record an EP of Italian songs in the original language just for the fun of it. All while wearing the most outre items in the designer dressing-up box. Onstage at least she's not a jeans and T-shirt girl.

Hairless Toys, released earlier this year, is her first proper record since her 2007 EMI album Overpowered. If it is weird, it's a good kind of weird: a confident slice of clever, shape-changing disco noir and through-the-looking-glass ballads (the title track in particular is a thing of rueful electronic wonder). So it's tempting to ask if the Mercury nomination comes with an accompanying sense of validation. "I think without sounding like a tw*t I was already feeling validated in the sense that most of my fan base reacted well to this record," she says. "But there was some concern from some other people that perhaps I wasn't making the right kind of record to come back with and so I had to kind of muddle through without everybody's full belief in what I was doing."

Who were these people? Labels? "Yeah, I've been to a couple of labels and they sort of snubbed it. 'We don't know if there's a market for it.' And I just had to ignore some negative comments. Nobody came in and said 'it's sh**'. But it wasn't being seen as a hugely commercial thing.

"But I honestly don't know what other kind of record I could have made at that moment. And I only ever make the records that are there for me to make that are correct in the moment for me to do. And that, more than me having two children, is the reason why I haven't made an album in those years. Yes I made this record of that track with somebody but none of those musical situations felt like the thing that was going to turn into the next Roisin Murphy album, you know?"

It was only when she worked with Eddie Stevens – whom she's known since her Moloko days – on the Italian Mi Senti EP that she realised her next collaborator was right in front of her. "We worked in a bubble. We had our vision for the record and we followed it. We're the vision people. When I did get negative comments, I kept this phrase in my mind: 'Don't tell the vision people what vision to have.'

"There's a lot of middle men in this world who feel they're equipped with numbers and strategies and what not, but actually they're just waiting for a real vision to come along and smack them in the face. I did have that in my mind. And without wanting to be arrogant about it I think we were genuinely explorative in what we were doing."

There is an unpredictability about the result. Songs start in one place and end somewhere totally different. It's the antithesis of the rigid structure of so much contemporary pop. ("It's either rigid form or lack of imagination," suggests Murphy.)

The temptation from the outside is to see Murphy's solo career as an exercise in frustration. Big gaps between albums. A constant changing of labels. An idiosyncratic talent never properly embraced. But that's not how she sees it. "I think I've had the exact career I should have had actually. I've had plenty of time to spend with my two children in the last few years and to discover that part of myself. That's insanely lucky. I look around me and I don't see many women who have managed to have both those things in tandem. That's been great. And in any part of my career I've only made the records I wanted to make and I've only released the things that I believe are good."

Yes, she's had the odd argument with record labels, but no-one has ever told her what to do. She wouldn't allow that. "My instinct tells me that if I gave up that autonomy and what I see as a kind of moral way of making music ... I would lose everything."

Anyway, maybe labels haven't always understood her (though she has nothing bad to say about her current one, Play It Again Sam), but then she's not always sure she understands herself. What she does know is that she has never let anyone dictate to her. Then again, no-one has ever tried to. "I have never had these patriarchal, crazy, 'let's tell her what to do' people in my life," she says.

"So whatever I do and don't have in my career is fully down to me. I'm in control of that at the very least.

"So," she adds, beginning to laugh, "I'm in control of how unsuccessful I am."

If you want a creation myth for this Roisin-ish wilfulness, maybe you could look at the 16-year-old she once was. Born in Arklow in County Wicklow (go to Dublin and turn left), her family moved to Manchester in the 1980s when she was 12. When her parents separated in 1988, her mother decided to return to Ireland. Murphy decided she didn't want to go and moved in with a friend. I'm not sure I would have been that brave at 16, I tell her. "I wasn't quite 16," she says. "I was still 15."

Right. Actually, that suggests there was a real core strength in the teenage you, Roisin. "There must have been, yeah. A self-reliance. And it was for very shallow reasons I didn't go back to Ireland. I did not want to go back to Ireland because everybody there was into heavy metal and I wasn't. So a Sonic Youth fan going back to heavy metal land was not on the cards."

Anyway, it wasn't as if she was alone. "I had my mates. I had my gang. The friends I had made were outsiders. And I was an outsider. That makes it a very, very strong thing. That's what's running deep in me. If you step outside the mainstream or the norm then you gain this great strength.

"I did that because I was bullied in school in Ireland. And when I left Ireland I felt this great sense of freedom. There was more choice. I had this sense that I can choose to hang around with people with their back-combed hair and their black drainpipes and their winkle-pickers ... all the 'weirdos' nobody wants to talk to ... And we found each other in Manchester. This is what you get strength from."

Was it the way she looked that caused her to be bullied? "No. I think my attitude was just a bit all over the place. Probably very sensitive. But very confident at the same time.

"I just felt a bit trapped at school. So in the end it was perfect timing for me to move to Manchester. And I wasn't about to let that go when I was 15. I'd gained it and I didn't want to let it go."

In 1990 she moved to Sheffield with a "half-a***d" notion of becoming an art student. At a party she met Mark Brydon. Her introductory line, "Do you like my tight sweater? See how it fits my body", was the beginning of a musical and romantic relationship, as well as providing a title for Moloko's first album.

"It was a sort of miracle that these two things happened in my youth; that I ended up in Manchester and found my way like that, and that I met Mark Brydon and we fell in love and out of that love came music. And that gave me something to do in life because I was bumming around a bit at the time."

She'd always had a voice. Family hooleys would hear the call for Murphy to sing Don't Cry For Me Argentina. When did she stop worrying about the Elaine Page comparisons? "I'd already signed a record contract. We'd done two or three songs with me chatting, pretending to be a valley girl in LA. That was what we got signed on the basis of. And then there was a tiny bit of singing in there and the A&R man really pulled us up on it and told us over and over again that I could sing. We went back up to Sheffield and started to write a song and sing it and I didn't look back from there."

The relationship with Brydon soured while Moloko were still a going concern, which meant the last days if the band weren't easy, but she still occasionally speaks to her former partner. "I haven't spoken to him for a good couple of years now. We're due a phone call."

She met the artist Simon Henwood when her solo career began (he provided the cover image for Ruby Blue) and they had one child together. Later she met the Milanese producer Sebastiano Properzi, which led to the Italian EP, a new relationship and a second child. Life and love and music are all tied up together in Murphy's world.

The Mercury nomination has been nicely timed for her return to the stage. She's looking forward to playing with a live band, recreating the complexity of the arrangements on Hairless Toys. There will be a visual element too: huge LED screens showing films she's made herself. "It's an interior of my head almost".

And then there will be a few costume changes. That almost goes without saying. "It is like walking on a tightrope as a performer," she says. "You've got one leg in a trouser and another arm in a skirt and you've got a mask on and a hat and a pair of glasses in your hand and your sock is hanging off. It really does get a bit Charlie Chaplin at times. But it's rare good fun as they say."

It's a cliché, she says, but walking on stage for the first time she had a realisation that this is where she was meant to be. "It's the best person I can ever be when I'm there."

As for this week, she will go to the Mercury Award ceremony not really expecting to win. "I'm just extremely happy that there's been a spotlight on the record. I'm absolutely delighted to be there and I'm going to dress up like a queen on the night and have a great time."

The winner of the Mercury Music Prize will be announced on Friday. Roisin Murphy plays the 02 ABC, Glasgow on November 24.