Libel and comedy

I have recently started writing comedy sketches for the radio, and in one of these sketches I poke fun at a couple of major fast food outlets. I have to refer to them by name, as part of the humour lies in the familiarity of the audience with these places.

I have read that libel is a defamatory or malicious statement made about a person in print. Does that mean I can get away with making fun of established fast food outlets on air?

The reason I ask is that venting hostility and targeting famous people or organisations seems to be a common element in a lot of comedy, whether it is stand-up or in the dialogue of a sitcom. Is it still libel when a comedian gets up on stage and makes fun of, say, President Bush? I see it done all the time in satirical comedy, and they always seem to do it without being sued. And yet a newspaper columnist or journalist can still be sued for printing the same kind of material, made in a less humorous way.

Thanks for the reply. I was just a bit confused as to what I could or couldn't get away with, after having seen satirists and stand-up comedians pretty much tear into public figures and organisations without getting sued.

For example, I often read a magazine here in the UK called Private Eye, in which this sort of thing happens all the time, and the reputations of politicians and celebrities are frequently battered in public. Quite often the dealings of large companies and media figures are accused of dodgy dealings or something similar within its pages.

I often wonder if I could get away with something similar. In my radio sketch, I make some truthful statements about fast-food outlets and their services in a mocking way. So since it's truthful and probably won't make a lasting impact on the reputations of these places, I guess I should just submit it anyway, right?