Tanith Carey: Nosey? Maybe, but don't expect PRs to say what's going on

Sad though it is for all concerned, the actress Kristen Stewart's frank confession that she cheated on her boyfriend, heartthrob Robert Pattinson, with a married film director does seem like a thrilling throwback to a bygone era.

After all, in this uber-cautious, post-Leveson age, where the most fascinating revelation we read about celebs is their shoe size, Kristen's confession of a "momentary indiscretion" is the language of an old-fashioned, caught-red-handed sex scandal – the type that once ignited our Sunday mornings when News of the World was still going.

Perhaps what is most surprising is that the pictures were published at all. In the current climate of fear among journalists, any faintly incriminating images involving a famous person are lucky to see the light of day in any UK newspaper.

Indeed, British celeb-watchers have had to make do with a sneak peek of the cover of the US magazine where they first appeared.

But then these photos of Kristen in the arms of Rupert Sanders, who directed her latest film Snow White and the Huntsman, were taken and published in America where the press is very much freer than it is now becoming in the UK.

Of course, there are those, arguing for privacy laws while we await Lord Leveson's recommendations, who will say Kristen has every right to a private moment when entangling herself with a married father-of-two in a public place.

Dare I suggest that if Kristen had chosen the relatively easy path of obscurity over fame – and spent less time posing on red carpets in fronts of stacked ranks of photographers – they might have a point.

But I fear she forfeited that with the mass of magazine covers and red carpet appearances she has made over the past few years. After all, celebrity is not a tap that can be turned on and off at will. If people are interested in you, they aren't just interested in what frock you are wearing or what cereal you have for breakfast. Funnily enough, they are interested in who you are sleeping with, too.

Of course, it's easy to dismiss the Kristen love triangle as inane tittle-tattle for people with nothing better to think about. But let us not pretend that the minutiae of these stories doesn't provide great entertainment. Who can forget the telling detail about Sven-Goran Eriksson's stacked shoes, or, most famously (and misleadingly, it turned out), David Mellor's Chelsea shirt? We devour these titbits eagerly, prurient though it may be.

But there's also a more serious point to be made. Now its days are numbered, is it such a good idea that the celebrity sex scandal vanishes for ever? After all, if celebrities have their way, they'd have us believe they live in a fairy-tale world of Hello! spreads – where if they aren't quaffing champagne at Nobu, they are feeding the starving in Africa.

More and more research shows our children's body image and confidence are being damaged by comparing themselves to images of celebrity perfection, unattainable without vast amounts of money, airbrushing and plastic surgery. Yet I am sure most celebrities who want a place on our pedestals would happily whitewash us into believing that they not only have perfect faces and bodies – they have perfect lives and relationships, too.

With the press on the retreat, these days, even the most minor D-list celebrities are surrounded by attack dog PRs and law firms only too happy to take advantage of an environment where they know many editors are worried about printing anything more controversial than a press release.

Ironically, instead of being the undoing of the people who committed them, sex scandals and kiss-and-tells have become the undoing of British popular newspapers which uncovered them.

No matter that the tabloid where I worked for 10 years, the Daily Mirror, was instrumental in the setting up of the NHS, campaigning for justice for asbestos victims and exposing seal-clubbing in Canada – the words sex and tabloid have become inextricably linked. And the word tabloid has become synonymous with sleaze.

But look at it another way and what is a kiss-and-tell but a modern-day morality tale? What could be more Shakespearean than a person with riches, fame and the world at their feet meeting their fall due to one fatal flaw? When the world reacts in horror to a betrayal committed by a celebrity, kiss-and-tells are welcome reminders that as a society there are still boundaries which are not meant to be crossed.

In Kristen's case, we are furious because she shattered the trust of the boyfriend who is supposed to be deeply in love with her and has also threatened the marriage of a man with two children. Our outrage is a reminder of what's right and what's wrong.

If we need anything right now, it's values. As it is, we are sleepwalking into an age dominated by an unregulated internet in the process of being taken over by porn. In this world, there are no rules to be crossed – women are routinely seen being hit and humiliated for sexual pleasure. There is not one word of censure.

So, having seen some degrading sights in my research for my books on sexualisation, it's faintly reassuring that anyone still cares a jot if the man Kristen Stewart is seen kissing is married or not.

Beyond that, if our press can't reveal the affairs of celebrities, it won't be able to reveal the affairs of politicians either. Mercifully last week, a judge acknowledged that the philanderings of a politician (unnamed) is still a matter of public concern (while ruling that the resultant offspring could not be photographed). It is a principle we – and those in charge of press regulation – must be careful to remember. How the men who rule our lives behave with their pants down tells us as much about their true nature as what they say when standing, flies zipped up, behind a ballot box.

David Mellor – a man you might expect to call for privacy laws after he was caught out (although not wearing that Chelsea shirt) with Antonia de Sancha in 1992 – pointed to France, where strict legislation has long prevented political scandals of huge public interest from being exposed: "It's extraordinary to think that but for an ill-judged lunge at a maid in a New York hotel, which was impossible to hush up, Dominique Strauss-Kahn might now be president of France."

The Mellor affair was one of the first nails in the coffin of the John Major "back to basics" Tory government. During the Leveson inquiry, it also came to light that Major persuaded his then Heritage minister not to resign because (or, at least, it must have occurred to him) he was worried it would set a precedent if his own adulterous liaison with Edwina Currie came out.

On the day, in July 1992, it landed on your breakfast table, it probably looked like scurrilous sleaze. But was there ever a more vivid illustration of the hypocrisy that can creep into the heart of power? Even today its repercussions are felt. It was a government which became such a laughing stock it paved the way for Labour's 13 years.

The fact is that our sex lives and the people we betray tell us more about ourselves than we realise.

Tanith Carey is the author of 'Where Has My Little Girl Gone?' (Lion Hudson)