Don't we adore politicians? When they're not dressing as snappily as Ozwald Boateng or telling the truth with the fervour of a man with a gun to his temple, they're ahead of a trend. Slogan T-shirts became fashionable in 1984, when Katharine Hamnett wore one saying "58% Don't Want Pershing" to meet Margaret Thatcher and Wham! asked to be woken up before they went went in "Choose Life" T-shirts. Then Frankie told us to Relax, and for a year most young chests were covered in bossy capital letters.

Then, last October, we suddenly had David Davis posing at the Tory conference (he was still hoping to be leader) with women whose T-shirts announced: "It's DD for me." The fashion tentacled through the parties, and now you can show your support for Menzies Campbell or Simon Hughes of the Liberal Democrats by wearing an "I'm a Minger" or "I want a Hughes one" T-shirt. Politicians! Don't you heart them?

Unfortunately, slogan T-shirts couldn't be less fashionable. They had a brief resurgence a few years ago with Madonna wearing a Britney T-shirt and Britney wearing a Madonna one and Nigella wearing a Delia one. But then came the super-naff French Connection campaign that gave us FCUK T-shirts. God, how subversive is it to pretend to misspell "fuck"? Mercifully the firm banished the logo from its clothing last year, realising it had shot itself in the foot (sadly not the head).

There are still slogan T-shirts which, like Hamnett's, try to alert people to political causes. Last autumn Vivienne Westwood designed a T-shirt for the human-rights group Liberty saying: "I am not a terrorist. Please don't arrest me." (Babygros saying the same thing will soon be available.) But it has since been widely copied, mostly in America, where some seem to think that simply wearing the message really does buy them immunity - with none of the money going to an action group.

The Fashion Targets Breast Cancer "target" T-shirt (OK, it's more of a logo than a slogan), has raised £6.5m in ten years in the UK, which must be a good thing - but it's an exception. Most modern slogan T-shirts are like those worn so often now at hen and stag nights: cheaply produced, worn once, and proclaiming a fibre-deep message.

If you have to wear one, no one's listening to you.