David Hare: The right stuff (enter, stage left)

It's too easy to dismiss him as a pampered pinko, with his tub-thumping repertoire, his smart Hampstead address and his fashion designer wife, Nicole Farhi. He once famously said of Tony Blair: 'I think he's me. I think he's us.' But now the establishment's favourite anti-establishment playwright has gone and put the PM on the stage, confounding, as ever, all expectations

How should we view Sir David Hare's new play, Stuff Happens, about the political events leading up to the war in Iraq, featuring Alex Jennings as George Bush and Nicholas Farrell as Tony Blair? Hare himself would have us believe it is an entirely factual piece of work, "a history play, which happens to centre on very recent history". In his programme notes he writes that the "events within it have been authenticated from multiple sources, both private and public". "What happened happened," he insists. "Nothing in the narrative is knowingly untrue." Yet he also admits to making up those frustratingly unknowable bits that occur in private. "When the doors close on the world's leaders and on their entourages, then I have used my imagination."

How should we view Sir David Hare's new play, Stuff Happens, about the political events leading up to the war in Iraq, featuring Alex Jennings as George Bush and Nicholas Farrell as Tony Blair? Hare himself would have us believe it is an entirely factual piece of work, "a history play, which happens to centre on very recent history". In his programme notes he writes that the "events within it have been authenticated from multiple sources, both private and public". "What happened happened," he insists. "Nothing in the narrative is knowingly untrue." Yet he also admits to making up those frustratingly unknowable bits that occur in private. "When the doors close on the world's leaders and on their entourages, then I have used my imagination."

And therein lies the confusion. If parts of the dialogue are "knowingly untrue", is it fair to judge and condemn the real-life politicians as we do their puffed-up, on-stage doppelgängers? At what point does fact become satire, and Hare's voice override the lines culled from published speeches and interviews? Should we trust Hare's job of compiling, editing and guessing any more than we trust Michael Moore to tell us the plain facts? So far, the critics have been divided.

Yet Hare is a subtle and practised manipulator of real-life voices, who increasingly believes that fact, not fiction, is where the most profound art lies. His most successful squaring of drama with reportage occurred in Via Dolorosa, his quasi-journalistic one-man show addressing the intransigence of the Israel-Palestine conflict. A cult hit in London and on Broadway, Via Dolorosa was based on dozens of interviews with key players conducted during a Royal Court-sponsored trip to the Middle East in 1997. It was a reinvention of sorts for Hare, who performed the monologue himself - and the beginnings of a method of working based on the assiduous research of individual testimony, "where the writer simply becomes a pane of glass reflecting truth and reality".

"People wonder about the real-life voices I use in my plays," he said last year of Via Dolorosa. "There are certain subjects where it's enough just to listen to people who know far more than you, and arrange their thoughts in a certain way. That isn't, in my view, any less creative than if a sculptor picks up a piece of driftwood and carves that wood and paints it... I regard myself as sculpting the stuff I find around me - which is the voices of other people."

It takes an artist at the peak of his creative abilities even to attempt to "sculpt" the voices of the world's most powerful men and women. At 57 Hare remains famously insecure about his reputation, yet the past 12 months have been some of the most productive and high profile of his career. After writing scripts for half a dozen poorly received films, he finally saw movie success last year with The Hours, the Oscar-winning adaptation of Michael Cunningham's Virginia Woolf-inspired novel, directed by Stephen Daldry, who also directed Hare in Via Dolorosa.

Then, earlier this year, came The Permanent Way, on the face of it an unpromising drama about rail privatisation and the Hatfield train crash - which, in its depiction of a crumbling industry driven by corporate profit, struck a chord with the public and played to packed houses at the National Theatre. Not since 1990's Racing Demon - the best of Hare's "State of the Nation" trilogy examining the faltering establishment - had he identified a richer vein of unease within British society.

Not that Hare has ever limited his scope as a writer, or lost his acute sense of moral certainty. He grew up in suburban lower-middle-class Bexhill-on-Sea in the 1950s, and was ambitious enough as a child to become head boy of Lancing College. He realises now that there was something deeply wrong with his parents' marriage, since his father, a purser for P&O, chose to be absent at sea for 11 months of each year. "I was very very disturbed by it. It seemed normal to have a father around and if you didn't have a father around, it was inexplicable." His mother "soldiered on", however, perhaps inspiring in Hare an appreciation of strong women that would later feed into his work in the theatre. In Hare's worldview, women are rarely passive and often represent a more virtuous alternative to male corruption (with the clear exception of US National Security Adviser Condoleezza Rice, played in Stuff Happens with particular severity by Adjoa Andoh).

At Cambridge, Hare was taught by the celebrated socialist historian Raymond Williams, while student protests against Vietnam raged outside the gates of Jesus College. At 21, he co-founded the Portable Theatre Company to take agitprop drama to theatreless parts of Britain, and began to collaborate with Howard Brenton. A succession of plays with appropriately radical and youthfully aggressive titles followed - Slag (1970), Brassneck (1973), Knuckle (1974) - yet Hare's concerns were never purely parochial. Sir Peter Hall writes of going to the ICA to see Fanshen, a 1975 play by Hare based on William Hinton's book about post-war Chinese peasants: "I felt as if my soul had been laundered by the end" - a sentiment that has perhaps haunted Hare's career hitherto.

Three years later Sir Peter gave Hare his first big break and staged Plenty, a portrait of disillusionment in post-war Britain, at the Lyttelton Theatre. Hare's relationship with the National was born. Today the country's best-known anti-establishment dramatist is the most-produced author in the history of Britain's state theatre.

Over the years Hare's leftist instincts have been tempered by the experience of observing politics in action. He believes The Absence of War, his 1993 play about the election fought and lost by fictional Labour leader George Jones, still "haunts" certain politicians. Before this latest war in Iraq, Hare was an undoubted Blairite - the recipient of one of the very first knighthoods awarded by Blair - and no fan of the hard left which sought to undermine New Labour. Once asked what he thought of the Prime Minister, Hare replied somewhat naively: "I think he's me. I think he's us. I think he's like all the well-meaning good people I know." In Stuff Happens, Blair is by no means a villain to equal the US hawks Donald Rumsfeld or Dick Cheney. Rather, he is portrayed as agonising over the decision to back a war clearly planned in Washington, although the odds he assesses are political, not moral.

In many respects Hare and the political theatre with which he is associated define the chattering classes. Obligingly for those who would seek to caricature him, he and his wife, the fashion designer Nicole Farhi, live comfortably in Hampstead and are described as both glamorous and enviably happy. Stuff Happens, too, lives up to the cartoon depiction of Hare as a pampered pinko, in that politically it is pushing at an open door. It will appeal to those whose ire has already been provoked by the war. While impressively executed, though, the issue has been so well chewed over that it will make few new converts.

To suppose that Sir David has turned his back on fictional theatre altogether would be wrong. Last year's entirely fictional Breath of Life, however, turning on an encounter between an ex- wife and an ex-mistress - despite co-starring Maggie Smith and Judi Dench - was widely regarded as one of his least meatily engaging works, as though Hare himself wasn't sure what it was supposed to say. And age has not dimmed his desire to make his voice heard. "I think of all theatre as political," he wrote recently. "The first question I ask a work of art is: 'What is it trying to say?'"