Taboos interest Belfast playwright Marie Jones. "The sort of things we are not supposed to talk about, things that are awful but funny and serious and true." Realities such as the fact people don't want to admit being embarrassed when middle-aged women talk about sex. Her popular play, Women on the Verge of HRT, which returned to Dublin this week, does exactly that.

When two women join the mass pilgrimage to the home of singer Daniel O'Donnell to participate in a giant tea party for his fans, it quickly emerges that their loyalty to him is more about the despair of lonely lives than his songs. "Give a play a name like that," says Jones, "people come to see it. Jesus, they wanted to see it before it was written because they think it will be funny. As soon as they're in the theatre, sitting down a few minutes into it, they realise it's going to be serious as well."

Jones, the writing talent behind the pioneering theatre group Charabanc, played Vera, one of the two women in HRT, during the play's three-month West End run. Vera's husband has left her for a younger woman so she has become engaged in an angry battle against her age, while her friend Anna is resigned to staying with a man she knows doesn't love her rather than living without a man.

"There's a line in the play when Anna refers to her daughter giving her the present of a holiday break with her husband and the truth is Anna can't bear the idea of being alone with her husband." Identification is a common response to her plays and Jones agrees she has never attempted to write a literary language. "I write about ordinary people. The people I write for are the people in my plays." Her approach is based on observation. "I think of situations and then I imagine how people would talk. When I'm writing the dialogue, I hear them speak in my mind. It's as if I was just listening to them."

Without sounding overly campaigning she makes the point that male sexuality is acceptable whereas female sexuality, "once that female has gone beyond a certain age", is at best pathetic and at worst slightly disgusting. "Life always has been easier for men. The women in my play are so desperate; Daniel O'Donnell gives them a reason to live."

Acting always interested her. As a teenager she wrote a letter to James Young, a well-known figure in the Belfast theatre world of her youth. Far more than a vague inquiry, it was an announcement. "I want to be an actor," she wrote. She was 16. Young replied he was about to begin auditions for a new play and invited her to come along.

"It was magic. He smoked those Manniken cigars, do you not know what I mean? They're small little things, like cheroots. Well there was the smell of them and also of stick make-up. I love it. It was," she stresses, drawing on one of several cigarettes smoked during the interview, "intoxicating. It was what I wanted to do." She got a small part. "I was dead chuffed."

What was the reaction like at home? "They were pleased for me." Up until then her notions about a life in the theatre had been met with the cautionary advice, "now don't be getting your hopes up".

Arriving at the stage door entrance of Dublin's Gaiety Theatre on a weekday lunchtime is atmospheric enough. It still has an old-world feel to it, and it is easy to imagine what it must have been like for generations of performers. The walk through the building is along a series of passages which are authentically dark and dusty, shabby and a bit musty. There is no mistaking it for anything other than a theatre.

Jones waits in an office. She is small, so short she feels the need to tell you in case you hadn't noticed. She has written 25 plays including A Night In November and has two currently playing in Dublin. Her latest, Stones in His Pockets, which takes place on a movie set and focuses on two extras in the film, has just opened at Andrews Lane in Dublin and also the Magic theatre in L.A. Yet she is more excited and a lot less world-weary than many writers in the throes of their debut. Having recently finished shooting a film of the life of mercurial footballer George Best, in which she plays his mother, her hair is back to her natural dark brown.

It's a strong, humorous, heavily-lined face, animated, very Irish, the sort you see in any town in Ireland, particularly in the North. Her accent is undiluted east Belfast, and few people can speak as quickly in complete sentences. Sharp and funny, her humour and her language are earthy.

Theatre had no place in her childhood home. "There was no history of even going to it. For me as a schoolgirl, playwrights were dead people. The first introduction to drama for me was at school." The youngest of three, Jones was born in 1951. Her father was a labourer in Harland & Wolff, her mother was a cleaner. "We were very poor, but so was everyone else, so you never noticed. I had a very happy childhood. I missed nothing. We only had a tin bath, so did our friends."

For as long as she can remember, Catholics were objects of fascination. "We weren't that far from them. We Protestants lived on the one street and across the road were the Catholics. On this side Protestants, on that side Catholics. Me and my friend used to go down and look in the window of the Catholic church at the end of the road for an adventure, to find out what they got up to with all the statues of saints and candles and throwing water over themselves. It was exotic and strange. We went in and felt they just had to look at us and know we were different. You see, we knew we looked like Protestants," she says with a laugh.

Jones points out that while it was possible for the middle-class Protestants of her youth to get by without being even aware of Catholics, for a working-class one it was different. "You'd see them. You'd be aware. You just didn't mix with them." Her abiding memory of that awareness is of fear - "fear of the Catholic Church and the control it had over life". It is a fear which lingers. "I don't want Protestants to feel threatened."

Asked if she hopes to see a united Ireland, Jones replies: "Only if something can be done about this fear. Protestants are frightened of the power of the Catholic Church, even now. You could say I'd like to see a united Ireland if it happened peacefully."

She left school at 16 "and went to work on the cheese counter at Littlewoods, like my sister and her friends. No experience is ever wasted." Office jobs followed and she enjoys saying: "I was never much good at that, but I was tolerated because I was considered good crack." While she "loved" her first experience on the stage, working by day and performing at night - "At that age you've so much energy. Sleep doesn't matter" - she soon became aware that while she was acting, "my mates were out chasing fellas. That's one thing about theatre, the anti-social hours." Describing her ambitions at that age she says, "they were about getting a fella and having a house with a bathroom. I wanted a garden. I wanted semi-detached suburbia."

At 19 she married her fella, "a hard-working lorry driver and had a baby at 21". Having got what she wanted, "including the white goods", she soon discovered "it was not enough". When Daniel was about a year old, Jones saw an ad in a paper, alerting potential members to a new drama group, the Young Lyric Drama Group. She joined.

"I was the eldest. Most of the others were about to go to university. They had come from very different backgrounds and were talking about things I had never heard of."

Jones recalls saying to herself, " `You're going to have to learn on your feet.' I loved it. I loved hearing them talk about art and books and music." It also made it increasingly difficult for her to settle into discussing babies, houses and white goods with the other mothers. "I tried though; I pretended, because of Daniel. I was quite good at pretending. But I was dying on my feet. I got very depressed." At 28, she walked out and left the marriage. "It's never easy for a woman to leave. Don't forget that was over 20 years ago."

All of this is said matter of factly, and while conscious of the shock on her listener's face, Jones, whose easy personality must conceal an obsessive commitment, makes no excuses for herself. She says she always knew Daniel would come back to her. He did at 15. Within a year, however, he had joined the Royal Navy. He is now a father. Jones has in effect two families. Her second husband is actor Ian MacIlhinney. They have two sons, now 10 and five. "It's great having young children at this stage, it means you get to do fun things."

Her experience with the Young Lyric Drama Group developed her confidence as well as her interest, and Charabanc, one of the most exciting theatre groups of the 1980s, was born when Jones and four other Belfast actresses like her got together. They were keen but not getting the work they wanted. "There was a dearth of good parts and even if they had been available we weren't getting them". In 1983 Charabanc approached playwright Martin Lynch, by then already author of Dockers and The Interrogation of Ambrose Fogarty and asked if he had anything suitable for the group to produce. As he felt his work to be more geared towards male casts, Lynch put it to them to try writing something themselves. He suggested they all write something about what it means to be a Belfast woman. The result was Lay Down Your Ends, which Jones co-wrote with Lynch. The title was inspired by a technical term used in linen-making, and the play tells the story of the Belfast linen workers' strike during which Protestant and Catholic women staged a walk out and attempted to form a union. Jones admits the play did follow Frank MacGuinness's The Factory Girls.

It is characteristic of her attitude that she makes no attempt to surround her work with mystery and enigma. Instead, she speaks about the revelation of working with Martin Lynch. "We had the same background, are the same age, the same experiences, the only difference is he is a Catholic."

Recalling the origins of Women on the Verge of HRT, she says: "A friend and myself were at some kind of theatre party; most of the girls there were younger than us. They tried to get us up to dance and we said, `careful now, you're speaking to women on the verge of HRT'. I thought it would be a great name for a play and said I must get down to writing it sometime and that was that for ages." But the title is not wholly original: the Spanish film director Pedro Almodovar's hilarious farce Women on the Verge of a Nervous Breakdown was released in 1988. Acknowledging that the Spaniard beat her at least to most of the title she says, "the HRT bit makes it a bit more topical".

Was there a single work which made her decide writing for theatre would be her life? "Miller's Death of a Salesman. It mirrors the whole of American society. For me that play proves that while Miller is writing the story of America it is mainly the life of that ordinary family which matters. And that's what I want to do: take ordinary people in extraordinary situations. Or at least, situations in which something has happened to change the life they had had."

A good example of this is her play The Hamster Wheel (1990) in which lead character Jeanette's routine of working in the school canteen and going to keep-fit classes each Thursday ends when her lorry driver husband suffers a stroke and becomes semi-paralysed. The theme - that of the virtual prison many full-time, non-professional family carers live in - is typical of the community-based concerns which marked many Charabanc productions.

But along with the social themes and the lives of women are the more obviously cultural ones. In 1991 she collaborated with Shane Connaughton on Hang All the Harpers, a piece which she had described as being about "music, culture, language and history". An important source was the 1792 harp convention in Belfast, which was not merely about playing harps, but was a highly-charged political event organised by the United Irishmen.

Jones does not conceal her loyalist background. "Of course we celebrated the 12th. For me and my friends it was an opportunity to meet boys. Lambeg drums were part of my world." Yet she has been described as having Republican leanings. Jones bursts out laughing. "I would like to see myself as a socialist."

In A Night In November, Jones risked a great deal - including being accused of political naivety - when she created the character of Kenneth Norman MacAllister, a Protestant dole clerk who delights in baiting unemployed Catholics, and who undergoes a radical personality transformation when he attends the North of Ireland v Republic of Ireland World Cup qualifier at Windsor Park.

In the company of his revoltingly bigoted father-in-law, Kenneth's eyes are opened and his stomach turned by the deranged hatred demonstrated by his fellow Protestants. Political judgments aside, Jones does not explore Catholic bigotry, but then it is a one-hander delving into one consciousness. It is a lively, skilful, often blackly comic and clearly-felt piece of writing. No-one could see the play as a rejection of her Protestant culture, but it is a strong criticism of aspects of it. Does she see herself as Irish or British? "It has taken me a long time to consider myself Irish but I do now. But that doesn't make me a Republican." Like many Ulster people, Jones remains amazed at the attitude of southern Irish people to the North. "It is not as simple as some would have you think. Nothing is."

HRT remains a favourite for her among her own works. Sitting in the manager's office at the Gaiety, Jones is delighted to discover a video of a documentary feature on it. The film contains clips. It is the production she appeared in. The camera frequently turns to the audience. The laughter is constant; she sits in her chair like a small child, watching her stage self on film, and is first with the lines each time.

Stones in His Pockets is set in the west of Ireland. It is her first play which does not have a Northern setting. The observation surprises her. "Aside of course from HRT, that's in Donegal. But you're right. That's the North too."

Is acting still important to her? "Yes, and I enjoy it. But it is harder to do theatre now with the children. But I'm a writer. It's what I feel I have to do. I'm delighted to be able to say I'm working when I'm writing because I enjoy it so much. I love writing, hearing those voices, making these people speak."