Stephen Poliakoff was once a mere state-of-the-nation merchant. Not any more.
On both sides of the footlights, the mobile phone has proved a major irritation. I recently witnessed a man coolly take the call he'd received in the middle of a play, so it can only be a matter of time before punters start making calls, too: "Hello, it's me. No, I'm fine. We're just approaching the gravediggers' scene. That's right, pop it in now on gas mark three."

On stage, meanwhile, the mobile has had a depressingly static dramatic function. Once acting as the easy shorthand for a yuppie (cue mechanical laughter), it's now a staple prop in attempts to update Shakespeare. Rare is the Shylock, these days, who doesn't learn that his enemy's ships have foundered via a phonecall. Any deeper thematic or plot potential in this noxious gadget (its implications, say, for our notion of civic space or privacy) has, however, gone largely unexplored.

To kick-start Sweet Panic, his new play which opens at Hampstead Theatre tomorrow night, the dramatist and film-maker Stephen Poliakoff shrewdly fastens on a double-edged feature of the phenomenon - the promise it offers of round-the-clock obtainability - and looks at how this may be changing the relationship between professional and client. Because she wants to get away from London for a complete break over a Bank Holiday weekend, Clare, a child psychiatrist (played by Saskia Reeves), tells a whitish lie to Mrs Trevel (Harriet Walter), the over-anxious middle- class mother of one of her patients, claiming that she doesn't have a mobile she can be reached on.

When she returns to work, it's to discover a long list of distraught messages from this woman on her answering machine and the news that the maternal fears weren't so unfounded. While staying with the family of a friend, the boy had gone missing for nearly two days. Far from calming down on his recovery, the mother gets stuck in a furious anger which she proceeds to take out on the psychologist, stalking her and confessing the wish to destroy her.

"You can imagine it with an American setting," says Poliakoff, "you know, Woman Against the System - the child killing himself and the therapist giving the wrong advice." He has gone, however, for subtler, more even- handed treatment. "I think a fussing, middle-class mother who doesn't work is probably the most unfashionable character you could put on the British stage at the moment," claims the playwright, adding that, though Mrs Trevel starts off appearing batty, her complexity and originality reveal themselves as the drama progresses and she manages to smash through Clare's mask of competence. This is a piece of equipment which professionals are forced to wear more and more determinedly these days, argues Poliakoff, as they scramble to keep up with accelerated change and to satisfy the demands of a while-u-wait society for speedier results.

There's a Thurber cartoon which shows a doctor, frowning in frustration, at the bedside of a female patient: "Your ailment is on the tip of my tongue, Mrs Cartwright - let me think." It's funny because honesty over haplessness is not the first thing you'd expect from a physician. "My sister's a doctor," says Poliakoff, "and, I mean, medicine is going through an incredibly complicated time because of the amount of new drugs available. People have to pretend they are in control. They're not."

Clare is not meant to stand for all child psychologists and she's no easy target: her creator is quick to point out that there's only an element of professional arrogance and glibness in her approach. But why a child psychologist at all? "It's like the canary down the mine - children are our indicators to what is happening. They pick up an extraordinary amount; they can smell our panic. That truth about the adult world struck me as very interesting. But another reason I went for a child psychologist is that you can become incredibly wound up by the professionals who deal with your children, fuelled by instinctive middle-class competitiveness." He has kids of 11 and five who go to the local state schools in Islington.

Looks-wise, Poliakoff brings to mind a chubby, rabbinical putto, with just a hint of Captain Pugwash thrown in. Peter Hall has said of him that "he always has an eye fixed on where society and fashion are going". While true, this makes him sound a little too like the garrulous "trend analyst" memorably played by Alan Rickman in Close My Eyes, his movie in which a combination of sibling incest, an unreally hot summer and the Docklands' setting created a powerful sense of something poised on the edge. It's important to remember, though, that Poliakoff is to Peter York what the prophet Elijah is to Russell Grant.

Occasionally, the eyes slide round to check your appreciation-level of a remark, but I must say I was expecting someone a good deal more bumptious and pleased with himself than the figure I met. Perhaps I'd been misled by thoughts of the renowned precocity: at 24, with an Evening Standard Award under his belt for Hitting Town and City Sugar, he was appointed as the first Writer in Residence at the National Theatre.

It was only after a slew of dramas about urban life that he turned his attention, in 1984, to his Russian-Jewish background with Breaking the Silence. While the Russian revolution raged around his private railway carriage, the play's protagonist (an amalgam of the author's eminent inventor grandfather and his electronics entrepreneur father) got on with the stubborn, selfish, admirable business of being the first man to put sound to film: a very pure image of the contradictions to which this dramatist is instinctively drawn. Playing With Trains (1989) returned to the topic of inventor, this time looking at how government and industry in Britain fail to back pioneering projects that are left to be commercially exploited by foreigners.

Shortly after this work opened, Poliakoff was taken out to dinner by a senior civil servant from the DTI. Their conversation focused his mind on a theme to which the play had made passing reference: that, with the increasing pressure for short-term profit, "scientists may not be able to stay within the tunnel of creative endeavour for long enough anymore". If this insight has fed into Sweet Panic, it has also produced Blinded by the Sun, a new play about scientific fraud that will open at the National in September.

"It's about science being corrupted by the same hype and showbiz as the arts. In government, in the City, even in the arts, you can lie and get away with it. Science is the one area left where it matters if you cheat, yet scientific fraud happens. People paint pretend sores on mice, in cancer research, the day before they are going to be inspected. To raise the necessary money, they have to hop on to spurious bandwagons: 'Ooh, look, my research is just like Jurassic Park.' It's about the purity of science struggling to preserve itself in a world that is getting more and more impure."

Meanwhile, the millennium looms, an event which, given Poliakoff's preoccupations, might have been scheduled just for his benefit. He has already given us a highly intelligent take on a turn-of-the-century ethos and atmosphere in his film Century. Contemporary concerns about genetic engineering and immigration were found in provocatively prefigured form in a story which took place between two New Year's Eve parties in 1899 and 1900. This does not mean that he's shot his bolt on this issue. To mark the millennium, he plans, for either the RSC or the National, a play that will have a number of smaller satellite plays orbiting round it to create one big work.

The way the past has been wrong about the future (and the lesson in that for the present) is one of his abiding interests. In Century, the characters visit an exhibition of would-be prophetic curiosities, misshapen ideas about the shape of things to come. In Sweet Panic, the middle-class mother obsessively collects newspaper cuttings of all-too-yellowing past predictions. You can see something like this operating in our perception of Poliakoff's own career. Early media commentators thought they had him neatly pigeon- holed as a Seventies state-of-the-nation merchant. They did not foresee that he would mature into such a variously vital writer or one whose speciality is confounding expectation.

n 'Sweet Panic' is at the Hampstead Theatre, London NW3 from tomorrow to 16 March. Booking: 0171- 722 9301