Kelly Osbourne: 'Don't you dare call me auntie'

"Dear Kelly, I've got a problem – I can't stop staying up all night, hosing down celebrities like you with my Nikon as they fall out of trendy nightclubs. Yours, Paparazzo, London."

That's not the kind of plaintive appeal Kelly Osbourne can expect anytime soon, either in the form of a phone-call to her BBC Radio 1 show The Surgery or for that matter as a letter to her new problem page, which begins on Saturday in The Sun.

As a friend of the likes of Kate Moss, Amy Winehouse and Lily Allen, Osbourne gets "papped" all the time; she was mercilessly boshed last month tottering out of Mahiki, then snogging her boyfriend recently in Café de Paris, and again last week while picking up Glamour magazine's Theatre Actress of the Year award.

"My personal life is made public to the world, which I find the most frustrating thing but, you know what, as far I'm concerned I sold my soul to the devil. I wanted to be famous, I wanted to do the TV shows, so you take the bad with the good," she says, rather graciously, of her relationship with the paparazzi. "It does come with the territory but I do think that in this country they're a bit extreme. The things they do to get the pictures they want are inappropriate, invasive and dangerous, especially when you're driving and have 25 flashes in your face. What if you hit someone?"

There is, of course, an apparent contradiction in Ms Osbourne, 23, emerging as the mass media's chosen counsellor of Britain's teenagers, a young woman who emerged into our collective consciousness as a 15-year-old member of MTV's The Osbournes, the jaw-dropping domestic adventures of those nearest and dearest to Ozzy, rock's own Prince of Darkness and resident of a mansion in Beverly Hills, California.

Since then, Kelly has grown her profile in Britain, most notably as a radio and television presenter, a star of the West End musical Chicago, and now as a ship's figurehead for the country's biggest-selling daily paper as it seeks to engage with a new generation of readers.

"I know I come from a very different background, people say 'Oh, she's over-privileged, she's this, she's that', but I know what it feels like to be alone, to be depressed, to have no idea what you want to do," she says, answering the question of the credibility gap before it has even been asked. "I can give good advice because I've fucking been there. Depression, drugs, you name it, I've been there. It's not fun and I was lucky enough to have amazing family and friends that have always supported me and brought me back from hell. When you wake up one day and nobody likes you and nobody wants to work with you. You're fat, you're depressed, you have no motivation and don't see the point in living anymore, that's when you realise 'I've got to change something'."

Osbourne sits in an office above the tailors's shops of London's Savile Row, just back from a long haul that saw her visiting her parents in Los Angeles and stopping off to see her boyfriend in New York. She has put her weight problems behind her, being so small and delicate that her shock of black hair, leather jacket, and rash of tattoos on hands and wrists give not so much as a hint of menace.

Which is just as well, given her role as a friend-in-need to teenage Britain. Barely out of her teens herself, Osbourne sees herself more as an agony older sister than a latter day Marje Proops. "The word Agony Aunt I think is demeaning to young people, because it's like a-gon-y aunt," she says crumpling up her face so that it ages five decades in an instant. "D'you know what I mean? I don't think there is a place within newspapers or magazines, in media all around really, where young people have a voice and can get what's on their chest off their chest."

Really? Aren't all these issues being thrashed out on Bebo and other youth-orientated social networking arenas? No, she says. "That's middle-class, because they have access to a computer that works and internet that somebody else is paying the bill for, and mobile phones and blackberries, that's people who have money to afford those kind of things. It's not the whole of England."

Osbourne, in spite of her time in California, embraces neither the Transatlantic accent nor the calculated aloofness typical of the international rich kid. She talks frequently of "this country" and appears to have a genuine social conscience. "I don't understand why when you are 12 years' old you are expected to be an adult but treated like a child. I don't think that's fair, there's this big vicious circle of 'Who am I? and 'What am I supposed to be doing?' and it confuses people.

"This country suffers from lots of young people with depression and at a loss of what to do. I went through that and have the greatest empathy and sympathy for it. It sounds bloody cheesy and corny but I want to make a difference!"

For her column in The Sun, Osbourne is working closely with the paper's head of features and entertainment Victoria Newton, though she responds to each problem personally. She says she took some time to find the right style, re-writing this week's column five times. "When I started, I was writing 'Well, there should be some stipulations...'," she says, in clipped tones that bring to mind Dr Thomas Stuttaford of The Times. "I thought 'What the hell am I talking about? I don't even talk like that.' I ripped them all up and did them again in about three minutes. I just sat there and thought, 'If that was me, what would I want somebody to say to me?'"

Not that she is unaware of the serious nature of her position. "I'm really, really careful about what I say because you don't know how stable they are, if it's as serious as they're making it out to be, and if you say the wrong thing sometimes it can have a bad ending. I have to do lots of research on what I'm saying, whether it's legal and the right protocol, because I'm not a doctor. If anyone writes in with a medical question the first thing I will always say is go to your doctor."

Her experiences on Radio 1, and now far with The Sun, have seen her becoming emotionally involved with the problems of some of her audience. "Sometimes it's really hard. One of the letters I had to respond to, was from this young girl whose mother died when she was seven and her brother was one, they had no money and are going to end up having to move to a hostel until they can get back on their feet. It was a two page letter and by the end I was in tears because it was so sad, she was only 11 and she was so smart, there was not one word spelt wrong in her letter and her hand-writing was beautiful," she says.

"You are leaving [the radio studio] in a taxi at half past 12 and you've just been on the phone to a girl who's 14 and pregnant and just been kicked out of the house with nowhere to go. It breaks your heart."

She is matey with other Radio 1 presenters such as Nick Grimshaw, Annie Mac and Fearne Cotton, and admires the studio know-how of Chris Moyles – "that's why he's got 8 million listeners every morning". Her own professionalism was recognised recently at the industry's premier awards ceremony, the Sonys, where she was nominated as a "Rising Star".

Osbourne has in recent weeks won awards from Elle and LK Today (for her style). She also has four television presenting roles under discussion, some in America and some here. Her manager is her mother, Sharon, though the daughter is quick to assert her independence: "We do very different things, she does X Factor I do teen advice." Sharon quit X Factor on Friday.

Kelly is convinced she does that advice better than some of the publicly-funded advertising campaigns that seek to make young people more healthy and responsible. "There's an advert on TV where there's this woman standing on a table, swinging her knickers or her handbag round her head. To me she looks like she's having a wicked time. It actually makes me want to go out with all my friends and get pissed, do you know what I mean?" she says, critiquing the recent Diageo "The Choice is Yours" responsible drinking advert.

"Some of these adverts are more funny than they are frightening. The one where it's like all 'Chlaaa-myd-ia, Gonnn-ooooor-hea' and it's like written on their belt or the label of their clothing and I'm, like, 'What are you trying to sell – belts that say Chlamydia? Or are you trying to stop people from getting it? I don't think they've discovered a way of speaking young people's language."

Osbourne admits she still likes the odd drink. "I'm not going to lie. People have labelled me as a party girl before. I think it's because of the people that I hang out with. But at the same time I'm not guilty. I do go out with my friends, as most 23-year-old girls do on a girls's night out, and get pissed, who doesn't?"

She also thinks she has a smarter way than the Government with helping young people to understand the importance of sexual health. "Chlamydia and self-harm and depression are the main things that we get letters on," she says. "If you catch something it isn't your fault, you've just got to do something about it and it isn't embarrassing to walk into a gum clinic because they see millions of people's private parts, it's their job. (Gum clinic?) Yeah, that's what they're called."

More than half of her correspondents are male, she says. "Women have a social group where they feel free to talk about all those kind of things, like girly gossip, but guys are too tough to talk like that so it's probably more men than women that write in."

Though she claims to have stopped reading the celeb magazines, she is a big reader of the tabloid papers ("What parts do I read? Oh fuck, the gossip pages! C'mon now!").

But for someone in line to inherit Ozzy's Throne of Darkness, Kelly Osbourne not only has a bright demeanour but is remarkably free of monarchical pretension, especially for such a paparazzi-pursued girl about town. Her down-to-earth, popular touch extends to obsessing over the real-life stories in the mass circulation Take A Break rather than dropping the names of the coolest style-orientated websites. "Cool?" she says, surprised. "No, I'm not cool. I don't try to do that."