Sophie Heawood: Leave the swearing to the toffs

My mother swears like a trooper. Actually, that's not fair – I grew up near soldiers' barracks and I never heard any of them explete like she does. Now it turns out that Keira Knightley and Madonna curse more than squaddies too, and they've both been told to bloody well stop it.

When on promotional duties for Atonement, Knightley got into trouble with the film's bosses for effing and blinding her way through the interviews, but last week she was at it again when talking about her latest movie, The Edge of Love. She used the F word; she used the S word; she used the C word; she swore as if swearing was about to be banned. Which it isn't, although Ofcom might wish it could be, after complaints came pouring in about Madonna turning the air blue at last week's Radio 1 Big Weekend. It's not the first time Madonna has caused such a headache – the BBC got a jolly good talking-to after she let rip too colourfully at the Live Earth concert.

But why does anyone still care about bad language? Surely it's a bit silly that society has chosen to imbue some words with a taboo, and now Mary Whitehouse has gone to the great censorship board in the sky, shouldn't we all get over it and let people say what they like? Well, you go and listen to seven-year-olds swearing at each other and tell me the sounds are pleasing to your ears. They aren't. So it is right to limit what words can be broadcast.

What people really seem to care about is that somebody like Keira Knightley, a fragile English rose, can use such naughty words. And how Madonna, so stately these days, and so close to 50, can be so rude. Well, it's obvious – swearing is posh, and it keeps you young, two things that Keira is naturally, and that Madonna dreams of being. Why we don't expect Keira to swear, I have no idea, because English roses might have porcelain skin but they have the constitution of lacrosse sticks combined with horses. They're as tough as old Russell and Bromley boots. (Don't forget, lacrosse originates in a game of war.)

Meanwhile, Madonna is aspirational posh (she married the son of a Tory Kensington councillor and a baronet) and aspirational young (is that really the same face she had last year?). On the eve of her 50th birthday, she is upping the cursing count to keep herself rejuvenated. All those 50p pieces in the swear box, caused by her late-onset Tourette's, still prove a lot cheaper than Botox.

Blame Richard Curtis. Ever since Four Weddings and a Funeral opened with Hugh Grant's stream of invective, swearing has clearly belonged to the upper-class Brit. And Madonna, like any American arriviste trying to gain access to west London society, surely based her notions of Englishness on Richard Curtis films.

Meanwhile, Cherie Blair says in her diaries, serialised in the press last week, that she was annoyed when the film The Queen showed her swearing – she never swears, she pointed out. Of course not. She was brought up in working-class Liverpool, a grammar-school girl. It's boarding-school girls like my mother who curse like buggery.