Never the most political of playwrights, Alan Ayckbourn was left feeling distinctly uncomfortable by Thatcherism. He took an allegorical swipe at it in Way Upstream in 1981 and then came back to tackle it head-on in A Small Family Business, written in 1986 though not premiered until 1987. In this he tackles public morality and how it gets skewed into its precise opposite when exposed to the family values and business imperatives which were the joint pillars of Thatcher's project. From the moment you start nicking the family firm's paperclips you are, says Ayckbourn, on a slippery slope that leads inexorably to throwing in your lot with a Mafia drugs cartel.

Certainly the moral - and dramatic - logic is clear in this tale of Jack McCracken, the small businessman coming in at the age of 45 to take over the family furniture business as his old, increasingly demented father-in-law retires. Unwisely, he makes a speech about the need for absolute honesty and integrity to the extended family who are all involved with the business, shortly before being brow-beaten by the women into reaching "an arrangement" with a private detective to avoid the prosecution of his youngest daughter for shoplifting.

From there on the juggernaut becomes unstoppable, with one family member after another revealed as diverting the company's legitimate profits into their own pockets via a family of Italian spivs. The private dick is soon on to it and, being excessive in his blackmail demand, has to be silenced - a despatch which, thanks to a nice sleight of Ayckbourn's hand is achieved by the women who batter him to death in the bathroom. This leaves Jack with a cadaver to dispose of, in order to protect the name of the family and of the business, and the only way he can do this is by making the company's distribution network available to the Italians' drug ring. The final desperate image, to complete the circle, is of Samantha, the shoplifting, porn-reading youngest daughter, perched on the lid of the toilet, shooting up.

A Small Family Business is, as Ayckbourn has been the first to admit, very dark indeed for a piece which nevertheless lays claim to being a comedy, and the only way to play it credibly (as we can be sure was the case in the original National Theatre production) is to trust the writer implicitly and convey the truth of his characters and their words. In this West Yorkshire Playhouse production, alas, director Ian Brown seems to lose his bottle and pitch the play as boulevard comedy.

As Jack McCracken, Gerard Murphy gives a somewhat lumpen, 'trouble at t'mill' performance, a million miles from Ayckbourn's description of Michael Gambon, for whom the part was written and who, it seems, "moved very subtly from small English businessman to Mafioso capo". Amanda Boxer plays Jack's wife, Poppy, like Jimmy Clitheroe's Mam with a Carmen Silvera wig and a stage northern accent which is both unnecessary and unforgivable.

It's almost certainly no coincidence that the actors who shine like beacons amidst a cast of 13 are Peter Laird, with a portrayal of incipient dementia that's both deeply moving and extremely funny, and Charlie Hayes as the wayward adolescent Samantha. Both are time-served Ayckbourn actors from the Stephen Joseph Theatre and are clearly aware that their author is a man for the stiletto, not the bludgeon.

- Ian Watson (reviewed at Leeds' West Yorkshire Playhouse)