Cutthroat competition, vicious rivalry and a Machiavellian economy with the truth. Pushy mothers make politics look like kindergarten, confesses Celia Dodd
Days before my first baby was born I went to an NCT breast-feeding class where a nursing mother proudly showed off her five-month-old son with a lot of that irritating baby-snogging new mothers go in for. Poor thing, I thought - she must realise he looks like a frog, how embarrassing to be so besotted with such an ugly baby.

Then the truth dawned. New mothers are like Titania in A Midsummer Night's Dream, in love with Bottom in an ass's head - the rest of the world can see how ridiculous they look, but they're not in on the joke. I resolved not to look so foolish when it came to my turn. In the event the problem never arose, because luckily my son turned out to be the most handsome and interesting baby in London.

The unashamed bias of parenthood is perfectly natural and almost endearing within the confines of the immediate family. The problems only start when women who are all as deluded as each other get together and start comparing notes. Suddenly, pride in your own baby's ability to reach out and grab things makes the next woman feel terrible because her baby can't. By the same token, you've got your gimlet eye on what all the other babies are up to to make sure yours really is still the best.

What is at issue is not so much the child's prowess as your own performance as a mother. Blind faith in the first is undermined by grave doubts about the second. Groups like the NCT were founded to boost their flagging self- esteem. It all looks so cosy: women sitting around in each others' homes supporting each other and doing away with the isolation of modern motherhood. Ha! In my experience, mothers fall into three categories: blatant show- offs, cunning self-effacers and bare-faced liars.

Blatant show-offs go on about Suzuki lessons and toddlers' French and getting your child's name down for the right school. They say things like, "I know everyone thinks their child is bright, but Saul really has got the most amazing mind," and ask their children endless questions in front of other people to prove it.

We all do it when things are going well, but Anna, a graphic designer with three children, aged seven, five and three, is one of the few who comes clean. "When Phoebe was about 14 months she could recognise all the letters in the alphabet. It was a wonderful party trick to bring out this little toddler and say, 'And what letter's this, darling?' I knew it was really nauseating and made the other mothers feel inadequate but I just couldn't stop myself." At least you know where you stand with women like Anna. Blatant showing off like hers is galling, but everyone else is sneering at her, too. It's easy to see her off by letting slip that your five year old is reading The Hobbit.

Much harder to deal with are the fake outpourings of sympathy. The other women sound so understanding: "Poor you, I know just how you feel, Max is the same." But they are thinking: "God, what a terrible mother? No wonder little Alice is so neurotic. Max would never behave like that." I know because I've done it. And, from time to time, they can't resist an indirect hit with an innocent-sounding remark like: "Don't you miss her when you're at work?" Or: "Do you always give him food from jars?"

Then there's putting yourself and your children down - a very British habit and one that I'm particularly partial to. It makes you sound so nice and modest, and it's a brilliant way of deflecting criticism. Tessa, who lives with her two young children in Brixton, says: "In my group, there are a couple of women who go on about how awful it all is, what a mess their houses are, how their babies never sleep and how naughty their toddlers are. Talking to them used to make me feel quite heady with relief and I joined in with the isn't it all ghastly bit, until I realised they didn't mean a word. I'd let slip that my baby had slept through the night since she was eight weeks old. This other woman started spouting research which proved that babies who didn't need much sleep were more intelligent. I was gutted."

At the school gates things can be just as cutthroat. I used to engineer ways of peering into the other children's reading folders to make sure no one was on Book 8, until I found the best way to size up the competition is to help in class. And, of course, if my child isn't quite up to speed there's always a good excuse - he's a boy (slower developer), that little girl is only good at writing because she copies her brothers, and, anyway, I bet my son has more interesting dreams.

Apart from developmental landmarks such as the first tooth and first word, there are a million ways to score points: how much time you spend playing, how often you whack on a video, how stylish his (and your) clothes are. Mothers at home usually have a nice line in concern about their working friends: "Jane's having real trouble with Emily since she went back to work. Emily really misses her." But the knowing look gives the game away.

There is nothing I like better than a good disaster story - babies who never stop crying (especially second babies whose mothers were smugly in control with their first) and successions of unsuitable nannies. I don't want to hear about children who adore dim sum when mine will only eat fish fingers. And my heart sinks when a Christmas card arrives with a perfect reindeer (drawn by Katharine, aged five) when my five year old can't even hold the pencil properly.

We all know why morale flags - mothers are insecure, the achievements of motherhood are so indefinable and they do not receive enough support. Dr Julia Berryman, a psychologist at Leicester University's Parenthood Research Unit, believes that competitiveness is inevitable: "Society holds women responsible if things go wrong and that is a pretty strong reason why women check on their child's progress by comparing him with his contemporaries," she says. "Women now have this big responsibility, but they're not quite certain what they're doing and what should happen at each stage. So, they are dependent on those around them for information."

But it's not all bad. I've met women - well, if I'm honest, just the one - who makes me feel okay about my imperfect parenting. Somehow, she does not make me want to boast, but if I do, she wouldn't dream of getting her own back. Yet, I'm sure she is as convinced as the next woman that her children are better than anyone else's. The difference is she's learned to live with her natural bias and keep it in its proper place - at home.