She may be contempplating life as a senior citizen, but Janet Street Porter has no intention of growing old gracefully

OH no. Another cackle is coming. But at least they are getting easier to predict. Like a Native American with an ear to the ground, one can study Janet Street-Porter's vocal chords at a distance for the next guffaw, at least five words before it actually begins. The only thing that could stop it would be a contradiction, snagged on a swear word or a particularly violent vowel. But no, here it comes, like the 9.15 from Chippenham.

"I don't know how not to work. Ha, ha, ha."

Street-Porter is wearing a pink V-neck jumper that matches her lipstick. The once-trademark glasses are gone, courtesy of laser treatment in 2001, and she looks youthful for 62. But slightly harried. She has been working this morning; she will work again this afternoon. As a jobbing journalist, she writes two columns a week for the Independent and a monthly interview for Marie Claire. Since returning to the small screen via Paul Burrell's ego on I'm A Celebrity Get Me Out Of Here! in 2004 she has also enjoyed a near constant run of television work, including her role as a field correspondent on Gordon Ramsay's The F Word. She has slid less than gracefully into retirement age but has no plans to call it a day.

"I was talking to Joanna Lumley about this the other day," she says. "There aren't a lot of women of our age on television, so we get offered loads of work, which is a shame really. Well, I'm not moaning. Ha, ha, ha."

We are in a London restaurant mulling over such details when a menu gets placed in front of us. Its size hampers the conversation. Street-Porter grimaces and slams it loudly onto the table. "My generation is the first that is going to redefine what it is to be a pensioner," she says. "My friends and I have this fantasy of having our own old people's homes that won't be like the kind you have now on the edge of towns with the smell of wee and boiled cabbage. We're going to be buying places with helicopters on the roof and throwing lots of parties. We're not going to do things the way our parents did."

It might sound like teenage rebellion but it's not: militant maturity is at the heart of her new tome, Life's Too F***ing Short - a polemic written in response to self-help books, which she detests. "It's about valuing yourself in a society that's still geared towards youth culture," she says. "It's very much aimed at women from about 40 onwards who look around and just feel inadequate." It teems with advice on areas like job interviews ("If someone asks how old you are then f*** off"), on diets ("a total waste of time"), and on dealing with unresponsive partners ("just put the f***ing rubbish out"). She says she has kept every theatre programme since the age of eight, every address book, every photograph - many of which are reproduced in the new volume. Yet she claims to hate "memory lane".

"You're probably thinking this woman's f***ing lost her brain," she says. "But it's not meant to be serious. It's just me - I'm a mass of contradictions." The glaring one being that she has written a self-help book. "But with a difference," she adds. "Women in the public eye are generally dieting and having surgery and trying to conform to some incredibly impossible stereotype. I mean, Victoria Beckham looks like a f***ing stick insect with a boiled egg on top. I'm not putting myself forward as an alternative but people sometimes say I'm like a role model for women who haven't fitted in."

Of course, Street-Porter has fitted in, but never for long. She gets bored quickly, and moves on as a matter of routine. These days, she shoots like a pinball between her houses in Clerkenwell, Yorkshire and Kent. Over the course of her 41-year media career, she has bounced from writing to presenting to producing. She was head of the BBC's youth and entertainment features from 1988 to 1994, where she won the international Prix Italia for adapting an opera production, Vampire, for BBC2. As editor of the Independent on Sunday, she was responsible for a spike in readership, despite initial media criticism that she was inexperienced, overrated and the wrong person for the job. The experience convinced her that she didn't want to run anything ever again, but she'll take newspapers over the internet any day.

"Newspapers have a future precisely because they offer an overview and in-depth analysis," she says.

"I want to read something by people who are intelligent and who think before they start writing. I read people's blogs and it's all, Got up. Went through the house. Cat came through the cat-flap' It's pathetic."

She suggests in the new book, as she has in the past, that friends should be whittled down through an annual cull, and that the term should be used with caution. "I get worried when people say they're good friends with everyone at work," she says. "What if you get the sack? Very few of the people I've worked with professionally over the years have become friends." The main exceptions are her colleagues from Network 7, the short-lived Channel 4 series she created with Jane Hewland in 1987 - "a tremendous thing that took over our lives". Otherwise, she forms bonds through shared interests and hobbies. She didn't become friends with her sister Pat until both women were in their 50s. But it was only after Pat died of cancer in 2006 that she got a feel for who she really was.

"She had far more people skills than I will ever have," she says. "There were about 60 people at her funeral that I had never met and they were all really good friends to her. It was such an accolade that all those people came. Whereas with me, I don't know "

Viewing close friends as the "backbone to life" has made her less of an egotist, she says, but only to a degree. "You could call me ruthless, driven, single-minded and self- centred," she wrote in her 2006 memoir Fall Out, "and you'd be right."On the other hand, she is incredibly vulnerable. She broke into commercial radio in 1973, at a time when accents were still tightly clipped, and the backlash was almost immediate. One LBC listener complained that she sounded "as if she were eating a plate of spaghetti with a fork and spoon"; others described her voice as "cut-froat" as opposed to cut-glass.

When she began presenting The London Weekend Show on television in 1975, she inspired a wave of semi-savage impersonators, most memorably Pamela Stephenson on Not The Nine O'Clock News. "I was very upset by it all, very thin-skinned - there's no point pretending otherwise," she says. "What annoyed me was that they equated a working-class accent with a lack of intelligence. I had a shitlist of people I hated, and I suppose one of the reasons I became a producer was to get off the screen - that way I hoped people would see I was highly intelligent."

That need to prove her mettle began at school, where she was bullied. Years before she became a "yoof" writer for the Daily Mail or a clothes horse for Zandra Rhodes, she was a gangly six-foot teenager and the last in her class to wear a bra. If there is a ruthless streak today, it most likely began right there. "People were horrible to me at school because I was thin, very tall, and had vodka bottle glasses," she says. "I looked weird."

The main reason she and Pat didn't get on was their late parents, Cherrie and Stanley Bull, who ran their home, she says, on a "divide and rule" basis. Street-Porter was always seen as the high-achiever of the family and was encouraged by her father to study architecture, which she did for two years before dropping out and entering journalism. She pinpoints the day her father moved the family from Fulham to suburban Perivale, when she was 14, as the moment she started loathing him. But it was Cherrie for whom most scorn was reserved. In the two volumes of her memoirs - Baggage and Fall Out - Street-Porter outlines her revulsion in no uncertain terms. In her 2003 Fringe show, All The Rage, she off-loaded a boiling vat of hatred, lined with C-words, and rejoiced in her mother's death. It was more caustic than comical, and made few in the audience laugh.

"As I got more successful I would go back home for dinner with my parents but they wouldn't give an inch," she says. "You knew my mum was going to criticise what you were wearing and you'd just think, Get a life'. When I took up running she told me that I looked too thin, and that every inch off my hips was another wrinkle on my neck. I was like, f*** off. It was terrible."

She says she has softened to the degree that, if Cherrie were alive, she could survive 20 minutes without a major argument, but no longer. "After I wrote Baggage, I got lots of letters from women thanking me for saying the unsayable, that you don't have to get on with your mother, that it's perfectly possible to find them self-centred, demanding, jealous. I think I understand a bit more now why my mum was the way she was but I'm not going to turn out like that."

Her motivation for writing Life's Too F***ing Short, she says, was "to pass on how I feel to people", for posterity perhaps, or as a gift to the next generation. She doesn't regret having no children of her own. "I honestly didn't feel I had to validate myself by reproducing," she says. "I didn't want a mini-me." Instead, she nurtures other relationships. Her current partner Peter Spanton - a former restaurateur studying to be a counsellor - is the latest exemplar of what she describes as a compulsion for serial monogamy. In all, there have been four husbands: Tim Street-Porter, a photographer; Time Out founder Tony Elliot; Canadian filmmaker Frank Cvitanovich; and David Sorkin, an unemployed salesman, 22 years her junior. "I tended to replace children with husbands and get very obsessed," she says. "They were all very creative people, very demanding. When you live with someone like that, a child or even a pet would just be another thing you'd argue about."

Infidelity has been a constant throughout her adult life, and a factor in most relationships. Thus, she was already seeing Tony Elliot while still married to Tim Street-Porter; her marriage with Cvitanovich ended when he caught her with Tony James of 1980s pop group Sigue Sigue Sputnik; the actor John Hurt was one of many scalps she claims to have taken in her extra-marital moments. But other than Sorkin - whose story ran in a tabloid with the headline "Jungle Janet Was A Beast In Bed" - she has stayed friends with them all. Fidelity, she suggests, is overrated.

"I think you're faithful as long as you can be, ha, ha, ha. But when you get older, things change. I'm 62, so I'd be weird if I was out looking for sex every day. Most women want fidelity in a relationship, but if their partner treats them badly, or they just get a bit bored, it's not the end of the world."

And if the tables were turned? If her current partner decided to stray?

"Well, we're women," she says. "We'd like the double standard."

In what sense?

"Ha, ha, ha, ha."

Her experience as a woman - and particularly a woman in the media - informs much of the new book. "More women appear to be at the top now in media but it's still a pretty macho world," she says. "It's tough working in an office where ultimately blokes set the way of doing things, where you have a lot of unnecessary meetings, a lot of emails, and everyone has their ranking in the system."

It's a problem that concerns her less these days given her return to television. Appearing on I'm A Celebrity got the ball rolling in terms of job offers but the real pay-off was the sense of liberation. "I just think, What are they going to say about me now? That I'm old and wrinkly?' I don't give a f*** any more." The only sign that things might be slowing is her recent acquisition of a compost bin, and her plan to spend more time growing vegetables. "But I'll probably turn that into a career," she says. "Does it mean that I've mellowed? A little bit ha, ha, ha. Maybe not." And with that she's off again: "Ha, ha, ha."

Life's Too F***ing Short by Janet Street Porter is available now (Quadrille, £12.99)