With her languid charm and raucous sense of humour, June Sarpong is one of television's fastest-rising stars. Here, the queen of the Sunday-morning schedules tells Ryan Gilbey about God, Ghana and her relationship with a Labour MP

Welcome to the exciting world of youth television. If you have celebrated more birthdays than can comfortably be represented by candles on a cake, you may not recognise the landscape any more, but don't be perturbed. Uncle Mike Read, Auntie Maggie Philbin and overexcitable Big Sister Cheryl Baker may long since have vacated their posts, but, if anything, the new crop of presenters assigned to babysitting duties during those sacred hours of the parental weekend lie-in are a friendlier, less prescriptive bunch.

Saturday mornings have been a drag since Ant and Dec left for adult shows more puerile than anything they fronted for their younger audience, but Sundays have, for almost four years, been as safe as houses in the soothing hands of June Sarpong.

This 26-year-old giggling Tinkerbell, raised in the East End by Ghanaian parents, dispenses her fairy dust over Channel 4's Sunday-morning strand T4. She pops up between musical interludes to participate in lark-abouts disguised as celebrity interrogations, or to goof around with her cheeky cohort, Vernon Kay. The combination of Sarpong's plain good nature ("She never says anything negative about anyone," Kay insists) and her co-presenter's naughty-boy antics is a winning one that shows no signs of waning.

It looks effortless, I tell her when we meet for brunch near her south-London home. "That's because it isn't really work," she giggles. "It's just hanging out with your mates. The older viewers will be tuning in while they're hung over in bed. You have to give them something that's easy to watch while they're eating their toast."

To someone who has never seen Sarpong in action - though "in action" probably isn't the best way to describe a woman whose greatest asset is her almost exaggerated languor - the notion of watching a pair of well-paid twentysomethings "hanging out" isn't immediately appealing.

There is, though, an art to it, and the public responds unequivocally. That much is obvious when we go for a stroll on Clapham Common. Sarpong twirls around, singing "One Day I'll Fly Away" to herself as kites sail overhead; half her time is spent waving to fans and handing out greetings laced with chuckles. A painter with chunky dreadlocks approaches her. "You know what makes me laugh?" he asks her. "What?" she shoots back. "Your laugh."

He's right. It's something you have to hear once in your life - that immense, celebratory roar that makes you imagine party poppers and champagne corks, in much the same way that cartoon characters see stars and chirping birds when concussed. Her merriment draws you in, which is one of the keys to T4's success.

Another element that is crucial to the show's appeal, and to Sarpong's popularity, is that neither display any visible signs of kowtowing to celebrity. Sarpong admits to having been overawed by Nelson Mandela, but the prospect of Robert De Niro in a foul temper didn't faze her. "The PR warned me, 'Oh, he's in a bad mood.' I thought, 'Get real.' He's a fine actor, but he's not saving lives, is he? If I'm gonna be intimidated by someone it will be a doctor." She thinks for a second. "Or Kofi Annan." She turned De Niro into a pussycat. "I burst in there. 'Hi Bob, I'm June.'"

I'm sure he was melted by her confidence. But her appearance can only have helped. For a start, she sashays everywhere, which is always a good sign, as long as you've got the hips for it. She sashays into the restaurant; she sashays past a line of waiters who look poised to burst into a celebratory conga line. Somehow, she even seems to be sashaying when she is sitting stock-still in her seat. She has a frizz of black hair, from beneath which dangle two long red earrings, like miniaturised Christmas decorations. Rather helpfully, she writes down the names of the various designers whom she favours. Her glamorous red dress, studded with glinting silver motifs around the midriff, is by Kupende Kuvar. The scarlet pixie shoes are from Top Shop. The chunky bracelet is by Chunye Chu.

I nod along as she scribbles these names in my notepad, along with some bands that she thinks I should check out - Floetry, 4 Hero. When she has finished, I feel I should make some contribution to all this talk about clothes. I apologise for the orange Calippo stain on my white T-shirt, but she doesn't care. "Do they still make Calippos?" she chirps, before turning the conversation to great-ice-lollies-we-have-known.

There is nothing to distinguish Sarpong in person from her on-screen self; she still makes you feel like you're part of her gang. "You can be in my gang any day," she says, mock-flirtatiously. She gives me a squeeze of the hand, the first of many. It's easy to lose count of them, like the high-fives that she dishes out during moments of joy - when it turns out that we're from the same turf, or that her mother was a nurse at the hospital where I was born.

Or when I recommend to her a book (Girlfriend in a Coma by Douglas Coupland) that her friend gave her only two days previously. She's a big reader, she says. Or, as she puts it: "I'm one of those saddoes who's always got her nose in a book." She has started an informal book group with some girlfriends. She polished off Paulo Coehlo's The Alchemist in a day. "It's small. And brilliant." Now she's reading something a bit saucy. "Don't put what it is," she says. I ask if it's pornography. "It may as well be. There's sex in every other paragraph."

She was, she maintains, always a chatterbox. She was born in Leytonstone, East London, and lived on a council estate before moving to Walthamstow when she was 12. "At the time, the estate wasn't too bad. When we moved out, it got really rough, and they knocked it down." I know she doesn't mean to suggest that the estate lapsed into dereliction once the Sarpong family vacated the area, but she presents so convincingly the impression of being community-minded, of nourishing the space around her, that it's plausible that a place might feel her absence once she leaves. She raves, for instance, about her current neighbourhood. "They've got everything I like - a greengrocer, a butcher. I get really excited at the greengrocer's. 'Pound of apples, pound of pears.' They know what I like. They tell me when the cherries are in."

When she was seven, her parents split up. Her father, a property developer, took her big brother, Sam, off to Los Angeles with him. Sarpong stayed in London with her elder sister and their mother, a nurse who worked double shifts to make ends meet. She doesn't seem to find it remotely strange that Sam left. She tells me about the Ghanaian way of life. "In Ghana, if the family hasn't got any money, they send you to live with those family members who have. Lots of people there aren't brought up by their biological parents. Consequently you can feel everyone striving to do well, because so many of them have come from nothing."

Sarpong positively coos over her years at the well-to-do Connaught School for Girls. "I was the kid everyone got on with," she says. "I was friends with the nerdy kids and the cool kids. Whenever there was trouble, the teachers always asked me about it because they said I was the most truthful girl. I was kind of a hip goody-goody." Even at such a young age, she was aware that she came from a different economic background. Her mother had pushed to get her into the school, but for the most part her classmates were from middle-class backgrounds. "Their parents were doctors, headteachers. Good jobs. We weren't poor, but they had more than we did."

When she was on her way to school one morning, at the age of 15, she was hit by a car. "It was agony. At first I couldn't feel anything. A teacher who lived nearby put her coat over my body. She calmed me down, started cracking jokes. That must have made me relax because suddenly I had the worst pins and needles all over, like itching, like electricity. Then the pain in my neck started, and I was screaming." What she didn't know at that point was that she had fractured and dislocated her spine. The doctors who cared for her, who placed her in traction with 20lb of weights pulling her neck back into place for six weeks, didn't know that either: they figured it was a straight dislocation until someone noticed that maybe the scratch on the X-ray was, in fact, a fracture. Sarpong was admitted into the Royal National Orthopaedic Hospital, something she can still become visibly excited about. "On the journey there, they couldn't risk going more than 20mph. I had a police escort, dahling!" she whoops. That laugh again. A waiter looks up from the till with a smile, as though someone has just told his favourite joke.

The accident sharpened a religious faith that Sarpong had never really examined before. "Straight after I'd been hit, I wished that my mum could be with me, and suddenly she appeared. Then I wished that the ambulance would hurry up, and then that appeared, too. That's why I believe in God. I so believe in God! I did before, being from a Christian family, but not in any major way. I always went to church. But after that, I thought: 'Oh, yes.'"

Once she had recovered, her life took off in an extraordinary way. It could just be the compression of time intrinsic to any summary, but Sarpong makes her career seem like an accelerated response to the 18 months that she had spent in various hospital beds. First she went ahead with a work experience gig on Kiss FM, despite her family's objections. "Coming from an African family, education is everything. We're told at a very early age that we have no choice but to do well. When I decided not to go to university, my family flipped. They didn't want to hear about some Mickey Mouse profession like the media."

But she landed a full-time job out of it, and more followed: shepherding Whitney Houston and Puff Daddy at Arista Records, presenting for MTV, and eventually bringing some pizzazz to Channel 4. As well as the T4 gig, she has hosted Dirty Laundry, a discussion show about teenage problems, and the savage Your Face Or Mine, in which audiences vote on, among other things, whether a man's current squeeze is prettier than his ex. "It can be cruel," she concedes. "We actually got fined by the ITC. I think the problem was that I'd touched a girl's silicone, and then Jimmy [Carr, her co-host] said something rude."

There are no plans yet to leave T4, but Sarpong is making sure she has her hands full. She has been frank in the past about her workaholic tendencies, and has readily admitted that her relationship with the Labour MP David Lammy was defeated by their incompatible work schedules. She has started her own production company - "Lipgloss Productions" - and has written a sitcom about a single girl in Ladbroke Grove. "It's in the early stages. I've got some cool people helping me to modify it."

I remember that she has already used that word once, when describing how she came up with the idea for Dirty Laundry with her agent, before taking it to Tiger Aspect, where that production company "modified" it. I find myself wondering if anyone will try to modify Sarpong. I don't think they would stand much chance. She'd chew them up and spit them out. All with a sunbeam smile.