Halfway through her fruit salad, Maria Goos puts down her fork and scurries out of the dining room, a swoosh of orange cotton and fiery red hair. Moments later, she returns, clutching a glossy coffee-table book. The title is Cloaca. At first, I assume that this is some deluxe edition of the script of her play. Cloaca was a sensation in Amsterdam. It has been translated into French, Spanish and German. It has been chosen to open Kevin Spacey's inaugural season at The Old Vic. Why shouldn't an enterprising publisher give it such lavish treatment?

As she puts the book on the table in front of me, however, I see that it isn't a script at all. It's not even by Maria Goos. It's the catalogue from an exhibition by a Belgian conceptual artist named Wim Delvoye, which just happens to share the same title. 'This is a cloaca,' she announces. 'It's a piece of art. A very modern piece of art.' And she shows me an image of Delvoye's creation: a sprawling system of glass tubes and chambers, running with murky liquid. And I think I know what it is.

Food, she explains, is stuffed in at one end of Delvoye's machine. From here, it oozes through a series of transparent compartments which are sloshing with chemicals that mimic the digestive enzymes of the human body. And from out of the other end comes, with horrible inevitability, a form of artificial excrement. She flips the book open to a photograph of the artist standing proudly over a selection of his machine's products: great whorls of greyish  turd,  curled  on  the floor of the gallery. 'Cloaca,' she chuckles, 'is a metaphor for all the shit that's going through the play. The play is like a gutter.'

Cloaca is a dark comedy about male friendship. Its central characters are four college friends, marooned somewhere in their forties and beset by frustrations and dissatisfactions. Pieter is a bureaucrat who is under investigation  for  misappropriating  art  from   the council vaults; Jan is a politician who believes that the foreign office portfolio is just within his grasp; Maarten is a philandering theatre director; Tom a coke-addled lawyer fresh from a spell in rehab.

In their university days, 'Cloaca!' was their dormroom catchphrase - a frat-boy code word they adopted without inquiring too deeply into its significance. If they had taken the trouble to look it up in the dictionary, they would have discovered its three definitions: a waste-pipe that carries away sewage (as in the Cloaca Maxima of Rome); a privy; an organ into which flows the intestinal, urinary and reproductive discharges of fish, birds and reptiles. (A fourth definition - a cocktail of Coca-Cola and coffee liqueur downed by reckless Dutch students - has yet to be officially recognised.) 'When these men say it,' asserts their creator, 'they have no idea how accurately they're describing their own existences.'

Goos  has been  looking for  an  opportunity to employ the word in her work for over two decades. 'It's been in my mind for 20 years. I thought that if I ever started a punk band I would call it Cloaca. But I'm almost 50 years old. I don't think the band will ever be formed now. Although you never know...'

We're sitting in the dining room of her home in Amsterdam, which, rather like Goos herself, is decorated with bright, busy floral patterns. Her partner, the actor Peter Blok - who played Tom in the original production of Cloaca and is the voice of Shrek in Dutch cinemas - is upstairs, laying down a set of new floorboards.

The couple met in the early 1980s, when they were theatre students in Maastricht. Peter is the only person permitted to read her work before it reaches its first complete draft. 'Always at the same point, at about page 25,' she notes. 'It's always the same ritual. I give it to him, he goes into the bath to read the play, and I'm walking up and down the corridor trying to hear whether he's laughing.' His recommendations are always useful, she says. 'I wish every playwright could have an actor at home.'

Television made Maria Goos a household name in Holland. It also bought her the house in which her family now lives, and paid for its refurbishment. She can point to the exact place on the dining-room floor at which the money from one series ran out and the cheque from the next took over.

Her two serials, Called to the Bar (a drama centred around the staff of a small law firm) and Old Money (a 19-part saga about the rise and fall of a family-owned bank), secured high ratings, effusive reviews, and more gongs than there was room for on her mantelpiece. But once the awards season was over, Goos found that TV commissioning editors had grown strangely unwilling to discuss her next project. Big Brother- a Dutch idea, she observes, with a dolorous sigh - and other reality shows were winning high ratings for minimal budgets, making filmed drama serials far less attractive to the network's accounts department.

'They gave me all the prizes you can win,' she notes, 'but there was no work. No work. I could have done a hospital or a detective series, but we already have four or five or six of them, so what's the point? They liked what I did. But they didn't want to produce it any more because it was too expensive. It was very hard to be told, "We don't want you. We don't want you to write any more." It blocked me totally.'

The rejection hit her hard. 'I had a big depression for a year,' she admits. 'I was so depressed that my neighbour, who has a chalet in Switzerland, told me to go and stay there for the wonderful views and the snow and the healthy air. So I went there with Peter and the girls, and there was no snow at all. I was so fucked up and depressed in this little wooden house. It was awful. I was really thinking about getting divorced at that moment.'

So did the theatre save her marriage? 'Yes,' she concedes. 'And it also saved my love for writing. The television business is tough. It's always about money. Better not to stay too long in it.' She pauses for a moment, allowing us to listen to the sound of her partner slamming nails into the floor above.

Chekhov, she says, is her most powerful influence. (You might guess that just by looking into her garden, with its piles of chopped firewood, cosy tables and chairs, and trees strung with lamps.) 'His characters can talk about their shoes or about an uncle visiting the house,' she says, 'but underneath you feel their loneliness, their hunger to feel close to others, to feel a deep relation of friendship or love. He makes us feel that we are prisoners of ourselves.'

It may be a more comfortable professional world than television, but Goos does not consider everything to be rosy in the garden of contemporary theatre. The Dutch stage, she argues, is dominated by directors who are determined to impose signature ideas upon their productions, no matter how unsuitable they are. 'We had a Richard III recently, and at the end of the play the actor threw off his coat and he was wearing a bomb. He was a suicide bomber. I hate that kind of thing. We all hate it. But a small highbrow elite keep it going.'

Cloaca contains her riposte to this tendency: Maarten, one of the play's protagonists, is a theatre director fixated upon preposterous symbolism -particularly if it involves young actresses getting their kit off. 'Cloaca,' she reflects, 'has an understandable story with a beginning a middle and an end. That was a relief for a lot of people here.'

This relief soon developed into box-office success. In Dutch theatre, all plays only run for a limited season and there is no equivalent of a West End transfer. After its first fortnight, tickets for Cloaca were almost impossible to obtain. Despite this, Goos was still flabbergasted when she discovered that the play had been chosen by The Old Vic's resident producer, David Liddiment, as an opener for the new season. 'For Dutch theatre-makers,' she whispers, 'The Old Vic is holy ground.' A literal translation was prepared by the British poet, Paul Evans. Playwright and producer then hunkered down at Goos's dining-room table and thrashed out a final version. 'I'm not too good in English,' she insists, 'but I have a feeling for rhythm. Sometimes there was a word that didn't seem right. It didn't have enough syllables, perhaps, and would have been funnier with more syllables. So we sat down with big dictionaries and I gave him maybe five suggestions for some lines.'

The trickiest part, it seems, was finding the right obscenities. The c-word, for instance, peppers Goos's original script. 'We're an awful country,' explains Goos. 'Everybody says that word all of the time. Young boys and girls from five or six say it. My children say it. Even politicians say it on television.'

Selecting suitable alternatives proved arduous. 'It almost killed me,' she reflects. 'I was exhausted.' But by the time of the first read-through, the actors were using a script that sounded, to Goos's ears, as if it had been written in English. 'That was a wonderful moment,' she breathes. 'I was so nervous. For the writer, the first read-through is the opening night. I was so relieved when people started to giggle."

She wants to explain something about the dynamic between the four male leads of Cloaca, but maintains that her English isn't up to it. So she calls her partner down to help. The hammering stops. Peter appears. She makes her point in Dutch, and he attempts a summary. 'When men are all together in the pub, it seems as if they want to make a pass at each other. They want to gain sympathy, to gain respect, but they'll never say, "I like you so much". They'll try in other ways, with other tactics, to show off...'

'To be the most funny,' says Maria. 'The most alert.'

'Which is their way,' continues Peter, 'of telling you that I like you, that I like to be in your company.'

'It's a kind of performance,' adds Maria.

'And,' offers Peter, 'when those men are actors, it's even more extreme. Even more funny. Other men just draw back.'

So actors are like men, but worse?

'The emotional life of men, a few years ago, was an invisible thing,' argues Goos. 'It's fun to be on top, to have all this status and ambition. But on the other hand, it's not giving you a great emotional life. You can't be at the top of an enormous office and have a very close relationship with your wife and children.'

She lets loose one of her conspiratorial laughs. 'You know, when some young people saw Cloaca they said to me, "We are really going to try not to become like these men." It's a very moralistic play.' She wags her finger portentously.