It was a Saturday and we were in a crowded supermarket. My ten-year-old was hunting for bargains with me while the younger one, 9, insisted on pushing the trolley. He could hardly steer it but when the trolley slammed into my heels for the sixth time I began to think this deliberate. “If you do that again, I'll smack you.” The trolley was slammed into my legs yet again. “Right!” I said. And rapped him (not hard) across his legs.

The boy surveyed the fruit and veg aisle. Then, eyeballing me like Damian in The Omen, he bawled: “My dad's a paedophile! Please help me!” Shoppers froze. I went purple and trembled. “Ha ha!” smirked my son.

We've had other incidents since then. But now that he's a teenager, he is more self-conscious and suddenly very sensitive about me embarrassing him.

“Dad,” he says when I propose coming to watch him play football, “please don't watch me today.” Or when I turn up at school: “Dad, can you park round the corner?” I must admit that when he says that, I'm tempted to drive right up to his classroom. So what if my car is 25 years old and has two mismatching doors?

Apart from the fact that parents tolerate so much embarrassment from their children when they are small, what's particularly annoying about teenagers is that while they suddenly become sensitive about themselves (so sensitive that you, their parent, only have to breathe to embarrass them) they become even more embarrassing to you - first, by deliberately assaulting your dignity and, secondly, by creating extra embarrassment out of their own potential embarrassment. On numerous occasions it's been my kids' fear of embarrassment that's ended up embarrassing me.

My elder boy, 15, is big on this. Shortly after he started boarding school this year I made the mistake of greeting boys in his house. “All right, guys?' I said. What a mistake that was! “Don't ever speak to anyone again. It's just not done. Is that clear?” He scolded me so dramatically that he drew attention to both of us.

A similar thing happened last week on the Tube. A man's iPod was turned up so loud that everyone in the carriage could hear it. I was irritated and looked at the man. “Shut up!” shouted my son - to me! “What a rude child!” passengers seemed to think. “What a pathetic father!” The whole carriage forgot the music.

I've tried to clamp down on deliberate embarrassment. But it's the inadvertent embarrassment that bugs me. How do I stop it? “Do that again and I will embarrass you even more,” I now think. That's not very adult, though, is it? It brings out the rebel in me. I have an old car and the older it gets the more I want to keep it. I talk to strangers and the more my kids want me to keep my mouth shut, the more I simply want to talk to strangers. I know I'm not cool. But I also know that I'm not as embarrassing as some parents.

The trainer of my younger son's former local football team was an inspiring 19-year-old. All the kids respected him - he was a great footballer and a big, strong lad. But one training day, as well as his girlfriend and child, he had his mother with him. She was about 40 and wore a T-shirt that proudly proclaimed: “5H1T FAC£D”. She told me in a loud voice that she had been “pissed” at a kid's party the day before and got a black eye on the bouncy castle. “OK guys, gather round,” said the trainer. “Let's check tomorrow's arrangements. Mum, where's my membership list?”

“See - he's not embarrassed by his mum,” I said.

“That's because his mum's less embarrassing than you,” said my charming son. We left after getting the trainer, his mum, girlfriend and brother to help to push-start our old car.

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