Comedy / Heard the one about the rabbi?

"ARE THERE any gentiles in the building?" New York rabbi turned quick-fire comic Jackie Mason asks a packed and enraptured Barbican. "They're hiding," he observes triumphantly, as the silence fades, "they're afraid to admit it." From the side, Jackie Mason is a shrink-wrapped Walter Matthau; from the front he is a disgruntled tawny owl; from the back he is a paperweight. All round he is, it says here, the Queen Mother's favourite comedian, and, as anyone who has seen the Queen Mother sitting in the front row of the Comedy Store hurling baroque epithets and half- eaten digestive biscuits at those who do not come up to her high standards knows, Her Majesty is a stern judge of a funnyman.

Watching Mason on the Royal Variety Performance, or last week's Frost Programme, it is easy to see what she likes about him. There are some comedians to whom TV's tendency to chop their material into bite-sized chunks and cover it with breadcrumbs does a great disservice. Jackie Mason is not one of those comedians. In short bursts his rabbinical rhetorical flourishes and willingness to use a steamroller to crush a grape are often overwhelmingly funny. But in the course of an exhausting and ecstatically received two-and-a- half-hour show, they can get a bit wearing. The same goes for his tendency to milk a joke until it begs to be let back out into the field.

The big problem with this set is its subject matter. The hit Broadway show from which most of it is culled is called Politically Incorrect, and there are probably no two words in the English language currently less conducive to laughter-making. When comedians start to whine on about political correctness, you now get the same sinking feeling of being about to hear something you have already heard as when they first mention Star Trek.

It is such an easy road to go down that it's depressing to see such a robust and sharp-witted performer as Mason opting for it.

But in some ways it makes sense. Ethnic difference is Mason's bread and butter, and if he honestly feels that the thought police are trying to take away his right to comical generalisation, then no wonder he's so crotchety. It's just that the endless litany of stuff he's read in the papers ("I don't make up stories to be funny," he insists - but that's your job!) crosses the line from stand-up comedy to the sort of dreary monologue you'd swap bar stools to avoid.

Mason is much funnier wielding his prodigious comic armoury against prejudice than in its favour. When the mood takes him he can incorporate two or three different edges into a single comic thrust. "I don't like these ethnic jokes," he deadpans archly. "People are all the same ... except you sir - you look a little different." And his ethnic turkey- cocking is most piquant when garnished with a side-order of self-mockery. "Those neighbourhoods where there's no Jews allowed? Only Jews live there - they all think they're the only one."

His attempts at physical comedy - jerking his body back and forth in a grotesque parody of the conflicting imperatives of contemporary life - are not a great success. Nor are his attempts to speak in voices other than his own. Essaying the vocal styles of Alfred Hitchcock, Julio Iglesias and Yitzak Rabin ("People want him to give back the whole of the West Bank to the Palestinians. He'd like to, but he can't - it's in his wife's name"), Mason somehow makes them all sound the same. This man is in a two-way tie with Alfred Sisley as the world's worst impressionist.

Mason is at his best when standing still, spitting out guttural vitriol - "vicious bastard low-life putz" - like a pension-age Gerry Sadowitz. An admirably querulous individual, after spending 20 years in the showbusiness wilderness for thumbing his nose at Ed Sullivan on live TV, no one could begrudge him his current pre- eminence. Just don't ask him to go gentile into that good night.

Leeds Grand, 0113 245 9351, tonight.