KELLY'S dad had an affair with Kelly's mom's best friend when Kelly was three. Kelly, now 23, who hasn't seen her father for seven years, is describing, between sobs, how he took her along on his clandestine dates. Suddenly her dad walks out on stage to sit beside her. The Ricki Lake Show is broadcast at five o'clock every Wednesday. This episode explores the experiences of "Children of Unfaithful Parents"; members of the audience are then invited to pitch in with their views, as outrageously as possible.

A glamorous family therapist with monstrously teased hair, three-inch stiletto heels and blood-red talons encourages the weeping Kelly: "Tell your father about the pain that's inside you," she coos. The audience are more robust. "If he'd been my husband," says one woman, glaring at Kelly's unfortunate dad, "I'd have done what Mrs Bobbitt did." The audience cheer and howl. Kelly's dad looks nervous.

Ricki Lake, the 26-year-old hostess, bounces from person to person, brandishing microphone and family-sized box of tissues for those overcome by their emotions. In America, where talk-show hosts are cult figures, Ricki's ratings are now second only to those of Oprah Winfrey. In Britain, she is pulling nearly three million viewers every week on Channel 4, and her UK ratings are equalling and even overtaking Oprah's.

Nearly 30 per cent of Ricki's viewers are in the 16-34 age bracket - the sector most highly sought-after by television companies - and another 8 per cent are under the age of 15. A recent BBC survey confirms that children are turning more and more to soaps and chat-shows rather than "traditional" children's tea-time viewing. Ricki's five o'clock slot is well placed to pick up schoolchildren and students, and her show has been specifically devised to capture a young audience. "Everybody does the same topics," she says candidly. "What we do is, we take it from the young end - if Oprah does a show `My Daughter Dresses Like a Tramp', we turn it around and the title of our show would be `My Mom Thinks I Dress Like a Tramp'. We have a younger host, hip music, younger guests, younger audience."

Today Ricki is as feisty, sassy and bubbly as every talk-show hostess should be; but a few years ago her career had fizzled out and she weighed 18 stone.

Back in 1988, when she got her first big break auditioning for avant- garde director John Waters, her chubbiness was an advantage. "He wanted a big girl who would act like she was a tiny little thing," she recalls, "and I was very uninhibited, very outspoken and candid." So she bounced into her first lead film role in Hairspray, aged 18, playing giggly 60s dance queen Tracy Turnblad.

But roles for fat actresses are few and far between. Ricki worked in television for a year, bought a million-dollar Hollywood mansion, then found herself out of work and broke. "I had used my weight to my advantage as much as I possibly could but I reached a wall where it wasn't working any more. I couldn't control my career or my financial situation, but I could control what I put in my mouth, so I started with that. In April it will be four years since I started." She is now around eight stone lighter.

The new incarnation as a talk- show host came out of the blue. "One of the producers saw me being interviewed on television. They were looking for a young woman under 30 to front her own show. They picked me, for whatever reason. I just hought, wow, I need a job, yeah, I'll take it," she says airily.

It seems talk-show hosting is harder than it looks. "It's certainly harder than learning your lines and doing what the director says. I'm thinking a lot on my feet, remembering all the names and all the stories, moving the show forward, expressing my own opinion - it's so much more than just acting in a movie. Luckily I've always had the gift of the gab."

Apart from the heavy-duty gossiping, surely the most difficult thing must be stopping the guests and audience from going for each other's throats? "Sometimes when you get somebody who gets soooo upset or soooo outrageous it can be a bit scary," says Ricki, sweetly tactful. She refuses to admit that any of them could be obnoxious or thick (though some of them evidently are. Such as the anti-gay vicar who thundered "You! Ricki Lake! You worship your rectum!" when she told him she had gay friends.) She even thinks Oprah is wonderful. "Her show is brilliant. She's been nothing but nice to me. She's an inspiration to me, seeing how she changed her body and she changed her life. What a nice woman!"

Sedate British chat shows, where the presenter knows in advance exactly what each guest is going to say, are very different to the American free- for-all; but shows such as ITV's Vanessa, fronted by Vanessa Feltz, are edging closer to the US format. Radio has already taken a significant step with the launch of Talk Radio UK, a station devoted to American-style phone-ins. Nancy Roberts, a veteran of New York talk radio, has just launched her Sunday lunchtime slot on the new station. She believes that television will evolve along the same lines.

"When the presenter pre-plans I don't think it works," she says. "The only way to do it is to get up there with the audience and a mike. People need to talk and be heard; they derive something very important from the sense that their contribution is being listened to. As British media becomes more audience responsive, the format will catch on in television too."

Susan Fleisher, who edits Ricki Lake and Oprah Winfrey's shows for British television, agrees. "At some point there'll be a British talk-show like Ricki's - tastes are evolving that way. British audiences might not be as animated or hysterical as the Americans - but the content is certainly all out there."

Ricki, however, is not planning her whole career round chatting. "I think of it as a stepping stone. I want to make movies and maybe sing in the future." In the meantime she is grateful for her good fortune. "No one's more suprised than I am at the way the show's taken off. I can't believe it. Every day I find I'm pinching myself and saying Wow, when is this all going to end?"