Two years ago Jennifer Saunders and Dawn French became fixated with a certain television programme. Each day they would feverishly discuss the previous night’s episode: to the point, Saunders says, that they became “slightly creepy, obsessive fans”.

That programme was The House of Tiny Tearaways, their new on-screen heroine the Times parenting expert and clinical psychologist Dr Tanya Byron. It seems odd to imagine French and Saunders, the sardonic queens of comedy, glued each evening to a heavy, psychology-driven reality parenting show. But Saunders assures me that this – psychology, real life – enthrals her. “Case studies, psychology books: that’s my perfect reading,” she says. “I just like looking at why people do things. I think I have an obsessive fascination with psychology”.

So they invited Dr Byron to appear on their Christmas show. Saunders and Byron became close friends, and the unexpected upshot is that today they are sitting on a sofa together in Notting Hill, having co-written a new prime-time comedy series for the BBC.

It is about a monstrous, faux-concerned daytime talk-show host, Vivienne Vyle, whose guests’ complex personal problems are summarised in cruel, vulgar headlines such as “My son calls the wrong man Daddy” and “Wife a slapper? Lie detector reveals all”. Their timing is impeccable. This week Judge Alan Berg attacked The Jeremy Kyle Show (Kyle, Vyle – get it?) as “a human form of bear-baiting” after a man appeared in court for headbutting his wife’s lover on the daytime ITV show. The judge fined him only £300 and added that in his view the show’s producers should have been in the dock. Byron and Saunders have caught the Zeitgeist. Vivienne Vyle defines the Noughties and the modern preoccupation with pop psychology and emotional voyeurism.

We all know the type of show: the coiffeured hair, the pseudo-therapeutical asides, the American-style whooping up of the audience as they reveal a child’s DNA results live on air. The Ricki Lakes, Jerry Springers and Trishas are now a staple of the daytime TV diet, and given the luscious potential for dark humour it’s astonishing that no one has done this before: and the Byron/Saunders product is a very funny, at times quite brilliant, satire.

The idea was Byron’s, which is why she gets her name first on the credits. She began writing it as a novel several years ago after becoming spittingly furious watching an American talk show about postnatal depression. Byron had a friend who had suffered terribly from the illness, and who killed herself while her baby was still very young. “I looked at the way these weeping mothers were paraded on telly and this kind of pseudo-concern flashing across the face of this highly styled chat-show host . . . and I just remember thinking how it’s all so exploitative,” she says. “So I wrote this story about this woman who was screwed up, probably more than the people she was interviewing on telly.”

Some might be surprised at the idea of these two working together: Byron with her confident, clinical calm, Saunders with a reputation (among journalists at least) for being a reluctant interviewee and shy to the point of painfulness. Byron laughs that while working together Saunders often had conversations in her own head, which she would end by simply saying “yes” out loud. She would have to ask Saunders: “What did you just say, and what did I reply?”

Saunders says brightly: “I didn’t realise I had conversations in my head but I completely see it now. Tanya would say things like, ‘Why did that make you angry?’ and I’d say [does bristling body language], ‘I am not angry!’ ” It might almost have been worth making a reality TV show of this: Dr Tanya Byron inside the mind of Jennifer Saunders, live on air! Except, of course, that Saunders would rather toast her own eyeballs than subject herself to that. She describes the prospect of appearing on Oprahas “an absolute nightmare. I’d probably have to take a lot of drugs”. She doesn’t find it easy to talk about herself, and her appearance on Parkinson was described as “an historic moment in nondisclosure”.

Does she still hate being interviewed? “I used to really, reeeeally hate it,” she says, pulling a face, “but it’s not so bad now. There is that moment where you’re thinking, ‘Don’t freeze, don’t freeze’. I’ve realised that you’ve got to work out what you’re going to say before you go on, which is a huge leap for me.” She says working with Byron has helped. “I am better now, aren’t I?” she asks her co-writer. “Tanya is very good at saying the right thing. She’s a great confidence-builder.”

That a woman as successful as Jennifer Saunders should need confidence building at all tells us much about human psychology – and about television, a notoriously insecure business. Though Saunders has a forbidding image, I found her spectacularly down to earth, although a little remote at first. Confessionals just don’t come easily to her, which is probably more normal than not. It’s so much easier, she says, being interviewed as a pair than solo.

And Saunders is masterly in the lead role of Vivienne, a horror who tells her wretchedly damaged guests: “You disgust me and most of my audience”, before flouncing off to dinner at the Ivy while they are left, humiliated, to pick up the pieces of their lives. It was Byron’s idea to play the character relatively straight, and consequently the comedy is darker than much of what we have seen Saunders in before.

The show also features a backstage psychotherapist whose job is to provide aftercare for the show’s guests, but who is really there only so the production company can avoid being sued. At the beginning of the series he is a timid character, appalled by the reckless irresponsibility shown by the production team, but he is gradually seduced by television and we see his boundaries sliding as he starts to harbour ambitions for his own show.

Does Byron suspect that some real-life TV psychologists are putting their own careers before best practice? Sadly she sees through my attempt to get her to bitch about other psychologists. “I don’t know about that because I don’t know the people invididually, but I do know that a lot of kids are now choosing psychology as a degree because they see it as a way of getting on telly,” she says. “Being a telly psychologist is seen as the way forward.” Has she been asked to work for such a show? “Yes, I have been asked to do those jobs and I’d never do it. It’s not ethically appropriate.”

The pair had to sit through hours of daytime talk shows while researching the series. Saunders says she used to watch a bit of Trisha, Vanessa, Springer and Jeremy Kyle – “you felt a bit dirty watching it” – but thought the genre had died down. Recently, though, with the new emphasis on therapy, it has enjoyed a resurgence.

Byron believes that there is a benefit from such talk shows in that they might help to destigmatise mental illness and provide a community for people who might be on their own all day with children, and are at risk from depression. But she says the irresponsibility and the pseudo-therapy are hard to take: “There are some we watched where you’d go, ‘Oh my God, I cannot believe this’. There was one where a woman was being interviewed about something really fatuous, like not doing the housework, and a crawler was running along the bottom of the screen saying that six months ago her seven-year-old son had died in his sleep. There’s a sense that with the rapid turnaround of these shows you become slightly desensitised to the fact that these are human beings, and I wonder if the people making the programmes do too.”

Which brings us to Helena, another monstrous character in the show, deftly played by Miranda Richardson. Helena is the producer, a slightly deranged, hyperactive, amoral shell of a creature whose two-year-old can speak only Spanish because she never sees her workaholic mother, just the nanny. Helena doesn’t care about the guests’ problems, just the ratings: so the sleazier the stories, the better. The character was Saunders’ idea. “I have seen those people working in television,” she says, laughing. “That manic energy. They learnt it on coke and they can’t leave it behind. Everything’s going to fall down unless they’re that manic.”

Work/life balance is the burning issue of the day, of course: and Byron has two children, Saunders three. So it seems apt to raise the fact that Saunders and her husband, the comedy actor Adrian Edmondson, whose daughters are aged from 17 to 21, have just moved from their 400-year-old granite longhouse in Devon, with its acres of land, back to their home in London. Both are working a lot in the capital at the moment, so living there made practical sense. Saunders says: “We went to Devon for the kids, and it was a great thing to do because it gave me time to think about what to do next. Ade was working, too, and we realised we weren’t going to see each other, so we moved back to town.”

Does that mean they have given up country life, and the open space and the sheep and the pet horses that Saunders so loves that go with it? The answer is no. “We’ve still got the house there. We just used to use it for holidays and then we swapped, and we’ll probably swap back again.” But she says there are periods when her work/life balance is “desperate”, so they try to arrange it so that when one of them is working, the other isn’t.

Intriguingly, Byron believes that the increasingly isolated lives that people lead has fuelled the rise of chat shows in the mould of Vivienne Vyle’s. “Once people would gossip about each other over the garden fence, but we lead such isolated lives now, working like maniacs while trying to bring up kids, and not talking to each other any more because we live in such a paranoid world,” she says. “Voyeurism is part of human nature and if we can’t satiate it in our own community we’ll find it elsewhere.” She believes that what happened on The Jeremy Kyle Show will become more frequent if people are pushed to their limits. In America two people have been murdered by guests who appeared on such shows. “If you keep pushing the boundaries to get edgier, harder-hitting stories, then eventually you’re going to have a problem,” she says.

Saunders says that the urge to disclose everything about oneself seems to be catching. “We’re at a point where everything is getting a bit out of control. Everybody is now an Edina [her character in Absolutely Fabulous], falling out of a cab with her knickers off. It’s happening everywhere.”

It’s paradoxical that an actress not naturally given to disclosure is starring in a series about the 21st-century compulsion to disclose. But that is probably why it – and Byron’s work – so fascinates her. In interviews over the past few years Saunders has indicated that her time on screen might be drawing to an end, that she is weary of the 6am make-up appointments. French and Saunders have already said that their sketch-show format days are over.

But Vivienne Vyle seems to have refreshed her hunger for TV: and if there is a second series, she might remain on screen for some time to come. “There is a time when you think, you know, there’s only so much make-up you can sit through,” she says. “But I really enjoyed this and it’s very different from what I’ve done before. I loved doing it and I’d go on doing it.”

The Life and Times of Vivienne Vyle, BBC2, Thursday October 4, 2007 at 9pm

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