Marina Hyde: This week

There is, perhaps, nothing which so depressingly encapsulates the pathetic nature of British politics than the traditional scrabble to sign up duff celebrities to one's cause. And there's nothing which so neatly confirms a star's self-love as the belief that their patronage matters. Congratulations, then, to the UK Independence party, which this week followed its enviable acquisition of Robert Kilroy-Silk as a European elections candidate by getting an endorsement from Joan Collins. "I do feel that my country is losing a lot of what I grew up with," announced the erstwhile CEO of Colbyco. "I feel we are eroding ourselves to Brussels." Thanks. But really, best stick to tips on how to effect an at-home "facelift" by judicious use of Vaseline.

Even more tragically, Boris Johnson recently confessed that the Tories had been desperately wooing Joanie to join them on their campaign trail - as though she were an asset of the political calibre of Prince Metternich.

Frankly, any celebrity who stalks into politics crosses a line from which there ought to be no return in the eyes of the public. It's not just the blinding pomposity, although the assumption that anyone gives a toss what you think about fiscal policy just because you've been in an ITV Bank Holiday drama seems vain in the extreme.

It's the canon you enter into. By nailing your colours to a party's mast, you do not draw down the spirit of Olivier, or Burton, or even Jagger. No, say hello to your new counterparts: Davidson, Lloyd-Webber, Hucknall. Rantzen. This side of the Atlantic, you're not Marlon Brando sending an Apache woman to collect your Godfather Oscar. You're Mike Yarwood at a bit of a loose end after ITV have canned In Persons.

Consider the Boulaye Wars. Via her long association with the Tories, Patti, who hasn't had a hit in years, has found herself elevated some leagues north of Madonna among party faithful. Here's Gyles Brandreth describing her appearance at the 2000 conference. "We are lucky to have her. She's black and beautiful - not attributes with which the Conservative party is over-endowed." If only rival parties had considered the Tories welcome to her. But the next year, who moved heaven and earth to book Patti for their annual ball but the Liberal Democrats. What sort of political pygmies fight over Joan Collins and Patti Boulaye?

Or recall the preferred line of attack of the celebrity Conservative: the threat to leave the country if Labour comes to power. And yet, have we got shot of Stephen Hendry and Paul Daniels? Then there's Andrew Lloyd-Webber, still promising to take flight the moment tax hits 60%, but currently collaborating lucratively with Ben Elton, veteran of excruciating Mrs Thatchaaaaaa monologues.

In the history of British celebs wading into politics, then, there have been minimal bright moments. Xfm DJ Lauren Laverne (then in rival band Kenickie) dismissing the Spice Girls as "Tory scum", for instance, or Coronation Street star Shobna Gulati's willingness to actually tramp the Oldham streets on her days off, canvassing against the BNP.

But ulitmately, the only person ever recorded as being sadder and more puffed-up than a celebrity "activist" was Tony Blair, on the occasion of his Cool Britannia do at No 10. Embarrassingly impressed by the attendance of Noel Gallagher, of popular mid-90s band Oasis, the PM attempted to crack a joke about how he and Noel probably used different means to keep themselves awake on election night. Gallagher subsequently revealed he had thought: "Twat." Correct, of course, but then at the end of the evening, Tony was running the country and Noel was going home to put the finishing touches to the profoundly duff Be Here Now, his credibility forever dented by those worthy snaps of him sharing a chuckle with PM.

So stick to the day job, Joan, Jim, Noel, et al. And if you're not working, do something seemly - like watching telly.