Liz Hoggard: What's so lazy about monogamy?

It's Mme Vaillant's conservatism that is the most depressing

Not every relationship is wrecked by infidelity

Aren't men just a wee bit insulted too? Are they really such slaves to biology? Does the lure of fresh skirt overcome every other interesting human instinct? I'm talking about the new Shaggers Charter, proposed by French psychologist, Maryse Vaillant. According to Vaillant, men should stop being castigated for being womanisers.

In her new book, Men, Love, Fidelity, she argues: "Some men can spend the afternoon in a hotel with their mistress and come home to dinner with the family without any feelings of guilt." It goes without saying that Vaillant is a man's woman. She dedicates the book to "the men I have loved and those who loved me".

But do men really need a champion? With the news that Warren Beatty has reportedly bedded 12,775 women, it sounds like business as usual for the modern Lothario.

Of course, monogamy is a fevered topic. Arguably it is not a natural state – for either sex. "Coupledom is a performance art," writes psychoanalyst Adam Phillips in his book, Monogamy. "But how does one learn what to do together? How to be, once again, two bodies in public, consistently together, guardians of each other's shame, looking the part? Where do the steps come from?"

Everyone has the right to a private life within their private life. There are some grown-ups who let each other play away. What depresses me about Mme Vaillant is how conservative she is. These days it's women who are having affairs. Despairing of the lack of activity in the bedroom (and their husband's refusal to go to counselling), many fortysomethings have flings with younger men.

Not every relationship is wrecked by infidelity. Discovery of a transgression may actually effect change. What offends me about Vaillant is her thesis that a faithful partner is somehow lacking. The refusal of married men to be tempted by other women is merely a "symptom" of some deeper malaise. "Pathological mono-gamists" lack the strength of mind to take a mistress, she insists.

In her book, she quotes Josephine, who moans about her ex- husband. "I would have liked him to stray a bit. But no, he was too lazy. So who got lumbered with him every evening? I did." This is the bit that really made me spit feathers. Commitment isn't lazy. We choose to give up the bodies of others as a tribute to the one we love. We honour promises that we make if they are important enough to us. Yes it's bloody hard. But even Beatty has done it (today he's married with four kids).

If it doesn't work, I'd much rather a lover told me straight away. I hate Vaillant's charter of "cheating discreetly" and "lying with intelligence". Lady Antonia Fraser confessed all to her husband weeks after meeting Pinter. If we once loved someone deeply, they deserve the truth. No one is forcing you to be monogamous. There's a world of pretty people out there. If you want a Get Out Of Jail Free card for life, that's fine. The toxic bachelor still gets invited to plenty of parties.

Monogamy is about choice – like supporting the same football team for 40 years, or always shopping at John Lewis. It's knowing exactly how much fun and variety is out there, and choosing not to pursue it. But let's not over-inflate the sex. Vaillant is right: fidelity is not proof of love. It takes rather more than that.