At the start of his new series, Alexei Sayle's Merry-Go-Round, the comedian acknowledges that it's been a while since he was last on our screens (three years, to be precise). "What have I been doing in between series? Well, obviously I like to spend a lot of time staring off into the middle-distance, rocking backwards and forwards and humming. The BBC have been awfully good to me. They got me a job damaging dogs for Animal Hospital."

It is typical of the man's contrary sense of humour that he should turn his absence from the telly into the opening gag when he finally returns. "The optimum frequency with which comedians should do a series is every year. I do one every three years. My audience is literally dying off."

Away from the cameras, his spiky TV persona is toned down, the sharp edges blunted. As if to prove the point, the day we meet he is dressed casually in a white T-shirt and green trousers, rather than the customary, in-your-face, too-tight suit and larger-than-life boots.

Sayle still has an openness which many more glitzy, PR-schooled stars could learn from. He says he was never keen to fill in his gap between series with guest appearances on the sort of comedy panel-games that are spreading like a rash over the schedules. "I'm not interested in going on Shooting Stars. That sort of thing is ghastly." At this point, he pulls a face as if he's just stepped bare-foot in a cat-litter tray that hasn't been changed for a fortnight. "It's just horrible and ungentlemanly. It's a choice you make. If you want to be a showbiz insider, there are compromises you have to make, and I'd find that soul-destroying."

Even after five BBC series, he is quite happy to retain his outsider status. "It's a price worth paying. The BBC have been wonderfully supportive. I'm constantly amazed they keep allowing me to make my series. I exist as an annexe of the BBC. I'm down the road a bit from the main building, in a little hut."

Perversely, he seems most content when he's discontent. He revels in being difficult, in going against the grain. "I don't think people were that interested in what I was doing for the most of the 1990s," he smiles. "I've been in and out of fashion three or four times. But you get addicted to being an outsider. There was a period at the beginning of this New Labour government when it seemed they were going to do all kinds of sensible things about ecology and unemployment. I found it disturbing. If someone starts agreeing with me, I don't like it. Out of pique, I become something else.

"You come to value certain aspects of your maverick status. In this business, you spend so much time fighting and having disasters, that when things go well it's unnerving. It's like if the hard left ever came close to power, they'd be terrified."

At the age of 45, Sayle preserves an almost youthful sense of rebellion. He is motivated by that most old-fashioned of concepts - a political drive - although he is the first to admit that comedy is never going to make people storm the barricades. "I never thought agitprop could work. It might have worked for six months in 1917 when the Russians were rushing around in trains spreading agitprop art, but they got squashed very quickly. You can't radically change people's behaviour through Light Entertainment.

"All the same, just being unpleasant is in itself a novelty. I'm fighting against the pointlessness and the harmlessness of shows like Shooting Stars and The Fast Show. Some of it's funny, but none of it has any edge at all. It's the prevailing orthodoxy, so just by being nasty you're saying something."

This unreconstructed sense of political passion has caused Sayle to drift apart from some of his former colleagues on The Young Ones and The Comic Strip. "The only ones I'm still friendly with are Lenny Henry and Peter Richardson. I've said this before, but I obviously thought we were more counter-culture than they did. I was amazed by how quickly they embraced the Oxbridge types I thought were supposed to be the enemy. When Mel Smith, Griff Rhys Jones and Stephen Fry all turned up as guests, I said, `What the hell is going on? Don't we hate these people?' I was also amazed by the rapidity with which they went for that whole showbiz bit. Now their petit-bourgeois roots are showing, and they all send their kids to public school. I suppose I'm just a left-over hippy."

Some of this disdain for more mainstream comedy seeps through into Sayle's material - notably, in his trademark aggressive persona. "When that started, I was just trying to be different. Having a dislike of things is an easy way to show up the falsity of showbiz. It was a post-punk attack on that warm showbiz persona."

Sayle's contempt for conventional showbiz types is also reflected in the pitiful figure of the bubble-permed, velvet-jacketed Scouse stand- up, Bobby Chariot. "Alright, how yer diddlin'?" he leers at a department- store security-camera which he hopes will record a showcase video for him. "Bobby Chariot here, top warm-up man and comedian. Separated from me wife, sleeping in me Jag, on pills for me nerves. Let the laughter roll - or even begin."

"It's about the utter awfulness of entertainers," Sayle explains. "I heard about one whose wife died in the afternoon, and in the evening he got into his Jag and went to do a gig. Their interior lives are so extraordinarily bleak. Laurence Olivier didn't even come close to it in The Entertainer. There are elements of that bleakness within me. I do like gloomy stuff. Also, you get inveigled into slagging off your confreres, and that only makes you look worse than the people you're slagging off. If you're going to do it, do it through your work."

Sayle takes delight in confounding expectations. "If I was watching me, I'd be a bit perplexed by the fact that I disappear for years, and then reappear," he laughs. "But I'd appreciate my complexity. And I'd always be looking for signs that I'd gone barmy or sold out."

What's the definition of selling-out, then? "Being photographed with Sting. When that happens, you'll know I've sold out."

`Alexei Sayle's Merry-Go-Round' is on Fri at 9.30pm on BBC2