Edwina Currie once said that if a man wanted to avoid catching Aids, he should take his wife on business trips. Perhaps a similar catchphrase could be made up for politicians: if they want to avoid affairs they "regret", they should take their wives to parties. For there are many. And these men are like kiddies in a sweetshop.

The nation woke up this week to the sight of a jaunty Deputy Prime Minister cavorting at the Whitehall Christmas party with his diary secretary, Tracey Temple. It turned out she had been his mistress for at least two years. This is the man who was believed to have the happiest marriage in politics: forty-four years with his loyal wife Pauline.

She was said by her husband to be "devastated"; the news came as a shock to her, at least. But not, it seems, to political observers, who believe that Prescott may have had a string of affairs. Many politicians do, and so do political hangers-on, journalists, PR girls, Westminster secretaries et al. I should know. My adulterous husband (Rod Liddle) is a political columnist.

Such people hang out in a world where affairs are the norm, the subject of gossip but not condemnation. Illicit liaisons spark up in the fevered atmosphere of rooms full of people who believe they are doing something important while spouting something clever, miles away from mundane family life.

My marriage broke up after I discovered Rod was having an affair with the receptionist at The Spectator magazine. This revelation was quickly followed by the news that the magazine's editor, Boris Johnson, had been at it for years with one of his writers, Petronella Wyatt. Then there was the astonishing news that the Home Secretary, David Blunkett, was having an affair with the magazine's glamorous publisher, Kimberly Quinn.

People like Boris and all the disgraced MPs and Cabinet ministers who have gone before are "at it" all the time because they can. They have the opportunity like no other working person in Britain, with perhaps the exception of army officers and lap-dancers. Not once a year at the office party but three, four, five times a week at the many functions that make the world of Westminster spin around.

Cabinet ministers have pulling power, there is no question. They can indulge all their mistresses' fantasies about power, wealth and influence. Even backbench MPs have more opportunity than most for extramarital affairs. Their wives are often left in the constituency while they are in London, staying in their second home, subsidised on expenses.

Pauline wasn't at that Whitehall Christmas party when her husband was so affectionate with a woman young enough to be his daughter. Perhaps she felt she had better things to do. Or maybe she wasn't invited.

Rod often told me that spouses weren't welcome at many of his parties. I don't know to this day how true that was. I don't think I would have cramped his style, as a journalist myself, I'm pretty used to talking to anyone.

As the wife of someone whose job it is to go to parties, it would be a bore to go to every one, but the occasional invitation to the more glamorous events would have been welcome. When I wasn't invited to the Spectator Christmas party - having written two pieces that had made the front page - I began to suspect something was wrong.

Later I learnt that Rod had spent the evening snogging his mistress like a teenager. I felt sick. Pauline Prescott must feel similarly nauseous after seeing the photos of her husband. Supposing she wants to stay with him, then I suggest she picks out her tartiest frock and forces her way on to the party circuit - whether he likes it or not.