A playwright would have to have a remarkably high opinion of himself to choose the word Gethsemane as the title of one of his plays. Even in this almost post-Christian country, the word still suggests what is most profound, tragic and numinous: Gethsemane is the garden where Christ watched and prayed all night in an agony of doubt, before accepting his coming self-sacrifice, and where his disciple Judas betrayed him with a kiss. To lay claim to one of the greatest stories ever told, as David Hare does in his new play Gethsemane at the National Theatre, is to risk an ignominious pratfall.

Hare can hardly be blamed for taking himself very seriously; most people do. He is a hugely prolific writer, seen by many as the brightest star in the British theatrical firmament, and adored by the left-liberal establishment. Notices of his Gethsemane actually appeared on the front page of the Guardian, in recognition of its great importance, and in the news sections of The Times and the Independent. Generally speaking, Hare is reputed to be as good as it gets on the English political stage.

In my view, though, this play, and very often Hare himself, represent precisely what is wrong with British political theatre - it is unsophisticated, uninformative and, worst of all, untheatrical. It is a waste of the great wealth of resources that have been so triumphantly amassed, in its actors, directors, designers, choreographers, coaches and schools.

However, it must be right for artists to be ambitious, even if they do overreach themselves, and Gethsemane does raise all sorts of ambitious questions. Its setting is very like the political court of Tony Blair, although Hare claims unconvincingly that the play is "pure fiction". There is a woman Home Secretary, whose career is threatened by a flaky husband who is facing trial for dodgy dealing abroad and by an enraged daughter who takes drugs. There is a smarmy Prime Minister who plays the drums (not the guitar) and sees himself as deeply religious while proving himself to be amoral, cynical and mercenary. Very close to the PM there is a fundraiser who brings Lord Levy to mind. And there is of course the press, snuffling out scandals like tasty truffles. Some gentlemen of the tabloid press (in real life) are given to saying "you couldn't make it up". In the case of the Blair imperium you didn't need to, and it seems that Hare hasn't.