Tulisa Contostavlos: 'It's not getting a job on X Factor that's hard – it's keeping it'

Tulisa Contostavlos is a member of the highly successful hip-hop outfit N-Dubz and is the new X Factor judge as well as, increasingly, a tabloid sensation. Over recent weeks the headlines have variously read, 'I was a teenage hell-raiser' and 'I took drugs' and 'I stole handbags' and 'I carried a baseball bat' and, most shocking of all, 'I lost my virginity at 14'. Tulisa, I say, I'm astounded. Fourteen! And you call yourself a Camden Town girl? I'm a Camden Town girl (originally) so feel I can ask you: what took you so long, love? Was it poor personal hygiene? Spots? Or were you just a late developer? There's no shame in that. She laughs and says: "Oh my God, where I was from 14 was normal." And: "I was second to last out of my friends to lose it!"

Is she 'a poor role model' as some have suggested? I don't think so. I think she's had a tough life, and is truthful, which is rather different. I also think she's totally terrific, and I say this as someone who doesn't much like young people anymore. "I don't much like young people, but I like you," I tell her at the end. "Thanks for being honest," she says. "No, thank you for your honesty," I say. It could have gone on forever – we could still be there! – but luckily she had a meeting to get to.

We meet in a pub in west London. She is 23, and gloriously pretty, with thick, dark hair, and exceptionally blue eyes. She has proclaimed herself 'the most famous chav in the UK' and her accessories do not disappoint. Her nails are fake, and bubble-gum pink. She has tattoos: a winged unicorn on her back and 'The Female Boss' along one arm. She is wearing a vest-top with the print of a Staffordshire bull terrier on it. She has, it turns out, a Staffie at home, and a Rottweiler. They are called Oscar and Josh. OK, I'm kidding. They are Prince and Kaiser.

I say: I don't think I'd like to be your postman. She says: "Oh, but they are sweet, not vicious at all." She seems wondrously clear-eyed about fame. "It's a pretty shallow world, isn't it? Why don't they have people studying for a degree on the front of Heat for a change? And the fakeness! I was told this week that I was being slated because I'd said I'd smoked weed. I said: Hang on. There are so many celebrities out there who do cocaine but you don't know it because they don't admit it, and these are celebrities whose posters are on kids' walls. At least I have the balls to stand up and say I made a mistake." A late developer, but terrific, like I said.

She is wearing jeans teamed with boots from All Saints. She says she has never spent more than £50 on an item of clothing. She has a curious relationship with money. She likes it well enough, she says, "because it's power". Because it makes other people sit up and take notice? "Because it makes me sit up and take notice of myself." But she doesn't like to spend. She has a house (in Barnet) and a car and says she doesn't want anything else. "I'm not materialistic. Ask any of my friends and they'll all tell you I live like a broke person." I say: What about when you go to an awards do, for example? No new frock? She says: "I'd rather borrow something and then give it back." What, I ask, about handbags? Now you are a big celebrity, don't you have to have a big designer handbag? Isn't there some kind of law about that? Isn't it, even, the first law of celebrity? She says she does have a handbag, yes. It's Louis Vuitton and cost £1,500. She says: "I did it because everyone was putting pressure on me saying: 'You can afford to live nicely. Buy something for yourself'." Was it worth the money? "I just wanted something that could sit in my room so I could think: I earnt that." Is it one of those ones with the 'LV' repeated all over it? "Yeah, otherwise how would people know it's not from Camden market? If it's designer, it has to be in-yer-face designer, right?" Do you think of yourself as a big celebrity? When you wake up in the morning do you think: 'Bloody hell, I'm an X Factor judge!' And then do you have to pinch yourself? "I pinch myself about everything," she says. She has come a long way. Or, as she puts it when I ask her if her family are proud of her: "Absolutely. They saw me at my worst and thought I wouldn't amount to anything because I was on such a wrong road. Now, they are all: Well done. You've done it."

we settle on a couple of chairs. She orders a basket of scampi. She invites me to tuck in. She flirts with the photographer. "I bet you're spicy after a few drinks," she tells him. (Probably not, but he perks up all the same.) She is wonderfully biddable, even though she's tired. She's come from another photo-shoot, and the X Factor auditions have been gruelling. "We can see 700 people a day." I say at least you have fellow judge Gary Barlow to look after you. I imagine him, I continue, as a poppet in a pinny always offering soothing cups of tea. Is he? "No!" He's a bastard? I knew it! I knew it!

"No. He's lovely, but because he is so passionate about his music he actually gets really offended if someone comes on and they are terrible, so he's the harshest judge." Why do you think Simon Cowell wanted you? "He wanted someone a bit rebellious." And they haven't bossed that out of you yet? "They don't tell me what to do." The next four months are going to make her stratospherically famous, and so I ask her: are you truly ready for it? She says: "If I'm not ready now, I'll never be ready," which she then amends to: "I was born ready". You know you won't be able to go for a pint of milk without being mobbed? "Whether I like it or not is a different story," she says, "but I will be able to handle it."

And what about the pressure on your appearance? Your outfits will be trashed. You and fellow judge Kelly Rowland will be embroiled in a fashion-off. One day you'll be too fat, the next too thin and, the day after, somehow too fat, but in a too thin sort of way. "I won't read it," she says. Really? You have that sort of self-discipline? She says she does. She says she used to read everything, but so much of it was rubbish she gave up. What's been written about you that's rubbish? "They said I trashed a hotel room in Miami, but I would never trash a hotel room. I always tidy hotel rooms before I leave." Always? "Always." 'TULISA LEAVES HOTEL ROOM JOLLY TIDY!' Nope, it's never going to make the tabloids.

Not a good role model? As someone who has endured personal tragedy and turned her life so entirely around, I'm not sure I can actually think of a better one. At nine years old, after her parents' divorce, Tulisa became the primary carer for her mother, Anne, who suffers from schizoaffective disorder. This is an extreme mood disorder during which periods of elation and hyperactivity – her mother might clean their one-bed council flat over and over – would alternate with depressed periods where she might imagine that the TV or hot water was out to harm them, so neither could be turned on. She was first forcibly sectioned when Tulisa was five, and at regular intervals thereafter. Tulisa made a BBC3 documentary (Tulisa: My Mum and Me) about all this a few years ago, which I happened to catch, and found extraordinarily moving.

When, later, I ask her about the most hurtful thing she's ever read about herself, she says it was when that programme went out, and someone said she only made it to promote N-Dubz, "and that I was a media whore". There is upset in her eyes, and she may be more vulnerable than we know. And kinder, too. Did your mother ever feel guilty about the childhood she gave you, I ask her at one point. "Do you know what," she replies, "I don't know. I've never asked her and I never would. I don't want her to feel guilty." She then adds: "I don't complain about it. I'm only talking about it because you bloody asked!"

I ask, too, where her father was in all this. Her father, Plato, is a musician and was an occasional keyboardist for Mungo Jerry. Her father, she says, "would always say to me I could go and live with him, but I always felt too guilty to leave my mum". I say I wish my father was called Plato; what a great name for a dad. "Not when all the other kids call him Plato Potato," she says, wearily.

She first attended a girls' Catholic school, where she was top of the class in pretty much everything – she is super-bright, I reckon – but had a horrible time. She was "strange", she says, "and under-socialised", because her mother did not like to be left alone, so Tulisa had to stay inside and rarely played out. The other girls didn't like her.

"I didn't have any friends. I was picked on, although in a fairly minor way. I'd not be able to sit in the lunch hall because I wouldn't be allowed to sit on anyone's table." At 13, she moved to Haverstock Comprehensive where she got in with the 'wrong crowd' although maybe, at that time, and in a way, it was the right crowd for her. I ask her if her 13-year-old self now feels like a different person. She says: "Yes, and I feel very sorry for her. Sometimes I think I want to go back and rescue her but then I had to learn to become the person I am now." You wouldn't be the person who could rescue her if you hadn't been through what you went through? "Exactly." Why do you feel sorry for her. "She was just very lost."

Her education went out the window. "I literally gave up. I just got so consumed with having fun and living. I'd been trapped with my mother for so long, and here were all these kids living miniature adult lives outside the home, and I was like: I want to do this. I want to be free." She drank (vodka and rum, mostly). She smoked weed (although gave up when she was 15, and never did harder drugs). And when she negotiated her estate, she did so carrying a baseball bat. Was that a pre-emptive move? So you wouldn't get picked on again? Did you become the bully?

"I wasn't a bully. I simply started to defend myself. And I became more defensive. If someone looked at me wrong, it was like: 'What the hell are you looking at?' Because I was so used to that look turning into something else." Is such behaviour based on insecurity, would you say? "Definitely." Perhaps this is why she also needs a Louis Vuitton bag just to look at. It symbolises: I am worth something. Whatever, this life did not make her happy, and there were two suicide attempts: one when she was 14 (pills) and one when she was 17 (she tried to slit her wrists). Where was your head at on those occasions, Tulisa? "I don't think I wanted to die. I was kind of like: I can't think of any other way to deal with all this. If I thought like that now, I'd want to slap myself."

How has she turned it round? Through strength of character – "I woke up one morning and thought: I'm not going to be unhappy anymore" – and because of N-Dubz. The band was created when she was 11; when her Uncle Byron, also a musician, put her together with his son, Dino 'Dappy' Contostavlos, and a school friend, Richard 'Fazer' Rawson. She has grafted hard ever since, she says.

"I didn't just sit around in my bedroom and wait to get signed by a record label. From 11, I was writing songs and saving money so I could put up videos on YouTube and going to pirate radio stations with holes in the floor." She has The Female Boss tattooed on her arm because she considers herself the boss of Dappy and Fazer, who can be most wayward. (If you have seen the Channel 4 reality show Being N-Dubz, you will also know that Tulisa's and Dappy's rows can be epic.)

It is certainly her job to keep them in check. The caring role, all over? "I definitely spent a long time being the mum of the group. Sometimes people used to say to me when Dappy was misbehaving: 'Forget about it. Stop telling him off. You'll drive yourself crazy'. This is the good thing about coming away from the group. Even before the X Factor we were all going to take a year out. I'm finally going to define myself, and I no longer have to worry: where is Dappy? What's he doing? If he now messes up, it's off his own back."

How do you get an X Factor job? Not down the Job Centre, presumably. "I met the producers and then flew to LA to meet Simon. He said he'd checked up on my stuff and liked what I was about, even though I can't really imagine him watching six episodes of Being N-Dubz." Are you nervous about the first show going out? "I'd be cocky if I weren't." And then: "It's not getting the job that's hard, it's keeping it."

She insists that fame hasn't changed her, and won't. "I just want to live a normal life," she says. That's going to be tough, I say. You'll get used to first-class treatment and all that. "I won't," she says. OK, I say, when did you last fly economy? "Two days ago when I flew Easyjet back from Magaluf." You win.

What does she like to do, when she's not working? She loves to read, she says, particularly Martina Cole, and a bit of Katie Price – "my guilty pleasure" – and is quite the little housewife, I think. ('TULISA: QUITE THE LITTLE HOUSEWIFE!' Nope, that's not going to cut it either.) She loves to do the supermarket shop. She says everything she puts in the trolley is like a little present to herself. And she loves her local Tesco in particular. "It's my favourite day out. I drag my boyfriend round it and he says: 'You could have done this on your own' and I'm like: 'This is our quality time'." You're not going to upgrade to Waitrose? "No way! Too expensive!" And can you cook? She can, she says, and she is mad about it. She is always trying new dishes and is currently into Caribbean cuisine. We talk about plantain and yams and scotch bonnets which, we agree, are the best chillies by far. "But I have to halve them," she says, "or it's too spicy." I can take a whole one, I tell her, so I think we both know who is the truly hard one around here. Fight? She declines. She may even be a bit of a softie, underneath it all.

The new series of 'The X Factor' begins on ITV on 20 August