Last month I used my column in this magazine to bemoan today's lack of proper pop stars, the ones who talk the talk as well as walk the tight-trousered walk, who know that the music's only part of the job and personality's the rest. Anyway, just days later, the editor called me up, all excited, and said, 'I think I've found you one!'.

Lily Allen was his answer to my rant, recommended to him by an OMM work-experience girl who had found her MySpace site. Lily had put up four of her chirpy pop-ska songs, and, within weeks, they'd spread like internet flu. She now has a staggering 24,932 friends on her page, Parlophone has rush-released her first single, 'LDN', and the limited edition seven-inch is reselling for £40 on eBay. Lily is a genuine, no PR, punters-love-it success, which is fantastic, but, even more promisingly, her blog is hilarious:

'Rudely awoken by the radio and that trollop Edith Bowman warbling on about how she is just BESTEST friends with just about anyone, so long as they are in a band and preferably wearing skinny jeans and stripey cardigans, and how the Magic Numbers are just absolutely brilliant, AGAIN.'

Funny and gratuitous: hoo-effing-ray, as my granny would say. Frankly, I couldn't wait to meet the little trollop-baiter. And here she is, muss-haired and make-up-free, in pink sun-dress and Nikes, sucking on a fag in a north London pub. It's 10am. Yesterday, Lily turned 21.

'I had a party on Monday night, at my house, with candles and caterers with mini hamburgers and a beautiful cake and everything,' she says, 'and then dinner for 10 last night as well. I got loads of presents, look ... ' She brandishes an impressive gold ring. 'It's big, innit? I dunno if I like it yet. I wanted one I could wear every day.' As her minder from the record company leaves, she starts teasing him about how the MD hasn't given her a birthday present yet. 'Tell him I like jewellery, gold, and 21-carat, none of your plate,' she grins. 'And some flowers tomorrow night would be nice.'

Tomorrow night is Lily's first ever gig, at a west London club run by her ex-boyfriend. Nervous?

'Yes, I'd be stupid not to be,' she says, not sounding nervous in the slightest. 'I don't want people to think it's going to be this amazing Madonna show. I've only done a week's rehearsals.'

Have you ever sung in public before?

'All I've really done is sung in assembly ... '

Whether she can pull off an outside-school live show is one thing, but on record, Lily's fresh; the beats are varied, from grime to jazz, her vocals, dreamy, with dark, funny, conversational lyrics. 'Words are really important to me. I'm not a real musician, I don't know the difference between a bass and a guitar, but I get really irritated if I can't visualise a song. I'll beat myself up over one line because I don't feel that it flows as a story.'

Lily's debut single, 'LDN' (pronounced London, non-texters), mixes giggly carnival summer reggae with a whistle-along tune and lines so sharp they could have your eye out. Plus it rhymes Tesco with al fresco, which is good. Part-novelty, part-brand-new, somehow 'LDN' recalls Althea & Donna as well as the Streets. 'Knock 'Em Out', the B-side, about blokes trying to pick up girls, is built around a Professor Longhair piano break and is just as entertaining: verse rapped, chorus ('You can't knock 'em out, you can't walk away ... ') sung as sweet as Sugababe pie. Then there's 'Alfie', about her little brother's louche lifestyle; 'Not Big', that discusses an ex-boyfriend's inability to satisfy; 'Everything's Just Wonderful', which manages to put worries about mortgages and skinny-bird stereotypes to a hey-groovy Sixties beat.

Lily can give you 'Smile', a bittersweet postbreak-up song, follow it with 'Shame For You' - 'Oh my gosh, you must be jokin' me/If you think that you'll be pokin' me'- and finish up with 'Nan You're A Window Shopper', a 50 Cent mickey-take, about how old ladies label all their kitchen jars and smell funny.

'I find it funny, that record company-speak of "How many singles have you got?",' she says. 'I mean, why don't you just try and do an album of 12 singles, instead of three? So that's what I did,' she shrugs.

Lily's live debut was when she was 12, a solo slot in front of schoolmates and their mothers. 'I sang 'Baby Mine' from Dumbo, the one the mum elephant sings to the baby. I made all the mums cry.' Though, actually, she thinks that the people she knew were crying because she was an angry, boisterous child and singing was the first thing she'd done that she was any good at. 'I was really rubbish at school. I had quite a turbulent upbringing. It was middle-class and everything was quite comfortable, but everyone was mental. I used to be really envious of those kids who could do their homework and bring it in on time and were organised.'

The mental people in Lily's life were, she says, her older sister and her younger brother, though, here, it seems apposite to mention her dad, actor, presenter and bon viveur Keith Allen. Keith left the family home when Lily was four, but is still a big presence in her life ('I speak to him on the phone like three times a day') and, though she was brought up by her mum, film producer Alison Owen, Lily is her father's daughter. She looks like him - brown boobly eyes, shit-eating grin - and she has his don't-give-a-monkey's attitude. 'I'm not scared of anything,' she states. She goes on holiday by herself, to India, Cambodia, Thailand, Vietnam; before she did that, she lied to her mother and stayed on after a family holiday in Ibiza. 'I told her I was staying with friends for a week, but I ended up being there an extra month. I wasn't staying with friends, I was in a hostel in San Antonio by myself, working for this record shop called Plastic Fantastic and selling Es.' Lily was 15.

It takes 10 minutes with Lily Allen to realise that she is one of the most self-assured women you are likely to meet. She seems predestined for fame: not through some lame X Factor desperation, or tits-and-teeth training, but because she's an original - fearless and funny - and because it suits her. She's born for the VIP area: such upbeat company she could single-handedly kill off the celebrity need for cocaine. Vogue is planning to photograph her and GQ and every other paper now wants an interview ... . and she sparkles so hard there's a backlash before she's even started.

On the internet, there have been rumblings about Lily's background, a feeling that she must have exploited her parents' showbusiness contacts to get where she is and that she isn't qualified to write about everyday life. 'Well, I've worked really hard for five years, my dad's never met anyone from my label, he's never even met my manager,' she states. 'It's annoying when people assume that you're handed something on a plate, when it's actually completely the opposite. They're all pussies in the record industry, they thought I was a risk. It's not a secret that I like to go out and have fun and also the music's quite reggaeish, and I'm a white middle-class girl, which they couldn't get their heads around. Anyway, if there's one famous person that's going to go against you, it's my dad. Unless I was Pete Doherty's daughter or something.'

Of her songs' subject matter, she says: 'I've been conscious to try and write about stuff that happens to people from all different backgrounds. Obviously I'm not going to go, I've been going to film premieres since I was five, it wouldn't make sense! People have said, "Who is this girl who's written stuff as though she's come off a council estate?" It's galling. I live in London, I read the Evening Standard on the tube.' Lily lights up a cigarette, fiddles with her multiple necklaces. We talk about really famous people. She saw Victoria Beckham in a brasserie the other day, 'and she did that thing that I hate, which is sending someone out before her to see if there were any paparazzi outside. While she was waiting, she was looking in the mirror, checking herself out, like this ... ' Lily pulls a ridiculous face. 'And she's so skinny! I was talking to a friend of mine about this weight issue for women and he said, "Guys don't like skinny women." And I thought, What makes you think it's about men? It isn't actually. It's more about women. 'Anyway, because I'm a bit of a fuck-off person, I want to be a bit chubbier than most. If there's going to be little girls listening to Lily, I'd like them to think "she writes good songs and she's also not saying we have to be skinny". No one looks like models except models: that's the whole point.'

Then she makes a suggestion about Posh Spice that is so lewd that I almost splutter my coffee all over the table.

As you may have guessed, Lily has no Beckham-beating ambitions. In fact, she's not sure that 'this' - she means making music - is her ultimate goal. 'I don't want everyone to think that I've arrived, because this might not be what I end up doing,' she insists, mysteriously. She says that, when she was young, she figured out that if she did 'the whole school thing' and went to university, she'd spend a third of her life preparing to work for the next third of her life, to set herself up with a pension for the next third of her life, 'and I was just like, "Fuck that, I'd like to make fuck-loads of money and then retire by the time I'm 30, please!" That's what I want, to have a really exciting block of about 10, 15 years, then marry someone with enough money, get a house in the country and have kids. I really want to spend lots of time with my kids and sit round the table every night and make Sunday roast and grow nice flowers.'

You don't have to be Dr Tanya Byron to work out that Lily's longing for stability is the result of her background. She was an unhappy child, attending more than a dozen different schools before leaving permanently at 15: 'I just used to fuck things up for myself.' She'd make the same mistakes wherever she went: finding kids of her age too immature, she'd befriend sixth-formers, who would then leave early to prepare for A levels, leaving her socially stranded. She couldn't concentrate on any subject she wasn't interested in, she ran crying from every exam, she never did her homework.

There was one teacher at one school she liked. 'He used to teach classical studies, and he'd tell us stories and it was just amazing. Greek mythology! I was mesmerised. But it's stories which are fun ... I can't remember dates. History: who gives a fuck? So you can sit down at a dinner party in 10 years time and go "Oh, in 1066, the Battle of Hastings ... Some treaty was signed ... or whatever."'

She can sound like a nightmare, though she says she was the easiest one of her siblings: her older sister, who her mum had at 17, was a wayward teenager, and her younger brother has attention deficit disorder. 'My mum took me to dinner parties, because I was the one she could do that with. I was really pretentious and precocious, people would say things, and I'd be like "That's really difficult, how did that make you feel?" and they'd be like, "Fuck off, you're only 10!"

After she walked out of school, Lily did a variety of jobs. Her mother and father instilled ambition in her, in different ways: 'My mum's not a handout woman. She always said, "If you want to go and buy expensive dresses and shoes, then go and earn a penny." And my dad calls me up every day going, "What have you written today, why aren't you in rehearsals, why aren't you playing live gigs?"' Before she found music, she worked as a barwoman, a florist ('I loved it, but the early mornings got too much'), even an actress: she got a bit part in Elizabeth (her mother produced it). At one point, she helped out at my friend's PR business: he, too, thought she was on her way to fame. 'Lily's not got a nervous bone in her body,' he says.

Still, despite her confidence, you only have to read her blog or listen properly to her songs to know that Lily isn't all gob: she wants to be liked, but by people she's interested in. 'I don't start hating people, but I just kind of grow out of phases,' she says. 'I was going out raving when I was 13, 14 and two years later I was like, actually, you're all losers and you're all taking ketamine and turning into heroin addicts and I don't want to be your friend any more. But I never burn my bridges with people, I just step forward to something else.'

Lily's self-sufficiency and grown-up attitude has led her into some odd situations. During the making of her LP, she worked in Manchester for a while, and stayed with ex-Happy Monday Bez, who's a friend of her dad, and his sons Jack and Arlo. At one point, Bez had to go to London for a night, so he left her to look after the kids. 'He said, just put them in a cab to school, make sure they've got their packed lunches, so I was like, "Yeah, cool" and then he didn't come back for a week! He'd ended up in Dublin or somewhere ... Still,' she considers, 'it makes a good anecdote.'

And Lily has her fair share of those. She met her first manager when he rescued her from some dodgy blokes in Ibiza: 'They pushed me up against a wall and tried to get all frisky with me.' Eventually he stole her mobile phone, called her mum and put her on a plane home. Something even stickier happened in Thailand that she doesn't want to talk about; instead, she tells a great tale about losing her licence through drink-driving. 'I tried to charm this officer at the station, going, "Been here all night?" And he said, "I just arrested you ... "

Lily's favourite book is The Other Boleyn Girl by Philippa Gregory. Her favourite films are The Blues Brothers ('the music bits') and Animal House. She's never fallen off a barstool but she's constantly weeing on her shoes ('weak bladder'). She can put her fist in her mouth. She cooks a good roast. She votes Green in local elections, Labour in general. She loves hip hop - Ty, Bubba Sparxxx, Three 6 Mafia - but she doesn't buy CDs, just records. She loves sleeping, too: 'That's why I don't get up to go to the gym.' The other day, her brother Alfie threw her laptop out of the window and broke it. What she was most annoyed about was the stickers she'd put on it. She'll have to get a new one but it won't be the same.

When you ask people who know Lily what she's like, they use words such as 'independent', 'highspirited', 'good company' and 'innately glamorous'. Ask her for five words to describe herself and she counts them on her hand.

'Not big and not clever,' says Lily Allen. We'll see.

Myspace: her final word

Lily Allen has already been called the poster-girl of the MySpace generation - in fact, OMM wrote about her briefly two months ago with reference to the revolutionary community networking site. She says the response to posting pictures and her blog and a handful of her tracks on the site was 'amazing ... but after a while you start taking it all for granted, because now I'll log on and have 120 messages like "you're amazing, you're brilliant", and you have to keep deleting them and you stop taking it on board.'

She thinks that 'a lot of labels - not necessarily mine - are run by older people and they're scared of it.' In fact, Parlophone had signed Allen before she put her profile up on the site - but it was her idea to do so and 'no one could have anticipated the level of attention I'm getting now, and that's purely because of the internet.

'But I don't want to be any kind of poster-girl,' she says, 'and I don't really want to talk about it any more. Obviously it's been amazing and I'm not ungrateful, but...'

Of course, OMM is now scouring MySpace for the next Lily Allen ...

· Lily Allen's debut album will be released by Parlophone on 17 July. You can hear 'LDN' and 'Knock 'Em Out' now by visiting her new website www.lilyallenmusic.com . With thanks to The Engineer