Edna O'Brien's latest offering has made it to the stage in full, flaming glory

When Edna O'Brien's first novel, The Country Girls, was published in 1960, her parish priest ordered his congregation to hand over their copies to be burned publicly in the chapel grounds. When its sequel, The Lonely Girl, appeared, her mother went through it, assiduously inking out any offending words. It doesn't really bear thinking about what they would have made of Triptych, O'Brien's latest play about a vampiric wife, her off-the-rails teenage daughter and her husband's sultry mistress, with its lashings of adulterous and underage sex and liberal sprinkling of the worst swear words in the book.

Now 77, the writer alternately garlanded by Philip Roth as "the most gifted woman now writing in English" and decried by the Irish government censor as a "smear on Irish womanhood" has lost none of her fire. "I wrote Triptych in a white heat," she tells me in her deep, considered brogue. "I'm not one for social niceties but neither am I one to be shocking just for the sake of it." That's as may be, but in the course of nearly half a century of writing, she has gained the dubious honour of being the most banned author in Ireland after her hero James Joyce and has lived in self-imposed exile in London for most of her career.

But even in her adopted home-town – where Triptych will receive its UK premiere at the Southwark Playhouse this week – O'Brien has had her battles. "The problem is getting a play on. It's much harder for a woman," she says. "I'm all for young writers but I'm also for writers who don't have to be young. What should be judged is the merit of the work, not whether it's by a black, white, old, young, gay, androgynous or whatever writer. The rigidity by which things are judged in our cultural world irks me very much. I would write a political play, I would write about Darfur if I knew Darfur, but I don't," she continues, building up to a charmingly delivered killer blow. "So – and forgive me for saying this to you, I don't mean it insultingly – I don't want to come as a journalist to a work. A lot of work that I see in the theatre is informed from the outside. I want to come to it as someone who knows it deep from inside."

O'Brien has long mined the rich seam of her own experience for her work. Born in Tuamgraney, Co Clare, she was schooled at the Convent of Mercy in Loughrea. In 1950 she qualified as a pharmacist and began work in a Dublin chemist's shop. Around the same time she bought Introducing James Joyce, a selection of the writer's prose with an introduction by T S Eliot ("a book that taught me more than any other about writing") and fell for one of her customers, Ernest Gebler, a Czech writer. Her literary fate was sealed.

It took her just three, intense weeks to write The Country Girls, the tale of two young women growing up in repressed, rural, Roman Catholic Ireland. Since then she has written more than 20 novels including In the Forest, her fictional take on the notorious Cregg Wood murders (a true-life case in which a mother, her toddler son and a local priest from Co Clare were shot by a youth on remand from prison), which further stoked the ire of her critics, and her most recent, The Light of Evening, a semi-autobiographical work about a mother who goes to New York in search of a new life before returning to Ireland (her own mother worked as a maid for a wealthy Irish-American family in Brooklyn for a time) and her glamorous writer daughter who marries a tyrannical older man.

In Triptych, three women fight to possess an absent, but powerfully enchanting male writer. His obsessive wife (Terry Norton), adoring daughter (Jessica Ellerby) and enthralled mistress (played, with pleasing symmetry, by Orla Brady, last seen grappling with a clandestine office fling in BBC1's Mistresses) swing wildly between being vulnerable victims and havoc-wreaking and self-destructive harpies while Sean Mathias' stylised and darkly comic production adds a touch of Desperate Housewives. O'Brien was inspired by Samuel Beckett's Play – in which a man (known simply as M), his wife (W1) and mistress (W2) stand in funeral urns and give their individual versions of an affair. "On adultery, it's probably the most visceral thing I've ever seen. When I was writing this, I had in mind that murderousness that passion brings out even in the best of people."

In the play, the wife crows at her rival that her husband is going to Spain to write the affair "out of his system". Does O'Brien believe that writing can offer catharsis? "Some relationships are so embedded in one's psyche, one's soul and one's mind that although they are written of, they are never written out of one's system," she says carefully. "Of course Triptych was triggered by relationships in my own life. But the challenge for me was to be the three protagonists – the wife, the mistress and the daughter." Though she refuses to elaborate – "He's just a man, no more horrible or more of a vagabond than many a man" – echoes of her own failed marriage resonate in the script.

When O'Brien met Gebler, he was married, a Communist and nearly twice her age. Needless to say, her parents (who were sent poison pen letters by disapproving locals) did not approve and the couple eloped to London, marrying in 1954. A decade later they divorced amid a messy custody battle for their two sons, Carlo and Sacha, and Gebler's sour assertions that he was behind the success of his wife's books. "The fact that my star, my little star, was rising, made him very angry," O'Brien admitted recently. "I think for writers – maybe for actors as well – marrying isn't the best idea."

O'Brien's love affair with the theatre has been more enduring, going back to her school days and the annual visits of the travelling players. "They did melodramas and the lighting was a row of paraffin lamps across the front of the stage but to me it was Stratford-upon-Avon or better," she recalls. "I had nothing to judge it by except that it was different from the fields and cows and horses and wild landscapes of County Clare. It was another world." In London in the swinging Sixties and Seventies she partied with Samuel Beckett (on one occasion, Carlo tested out his new palmistry book on the playwright, informing him that he had "a very thin artistic line"), and watched Peter O'Toole, Robert Shaw and Lotte Lenya working their magic on the stage.

Her first play, 1981's Virginia, based on the life and letters of Virginia Woolf and starring Maggie Smith, was followed by the family saga Our Father at the Almeida in 1999 and, in 2003, a version of Euripides' Iphigenia in Aulis. She writes the kind of plays she likes to watch. "I have a penchant for plays with no interval. I like plays that are around 85 to 90 minutes long (unless it's something profound like Shakespeare or Robert Lepage). A quick bullet – where what is omitted is equally understood, rather than going from A to B to C."

As our conversation draws to a close I wonder if O'Brien ever longs for the quiet life, an uncontroversial, non-priest-bating retirement from the quick bullets and white heat of writing? "They're all hell to write, I'll tell you that", she concedes, with a throaty chuckle. "But if it was easy, it would be a little bit boring."

'Triptych', to 10 May, Southwark Playhouse, London SE1 (0844 847 1656)