Mum, can I have my old room back for a bit?: Parents beware. You may end up with an Incompletely Launched Young Adult on your doorstep, says Isabelle Anscombe

Twenty years ago, parents would be slightly shameful and evasive about whether their children were 'living in sin'; 10 years ago, they might try to gloss over the fact that their daughter had just divorced; now, parents are fearful of a new but increasingly widespread sign of failure: the return of their twentysomething children to the nest.

For the generation that turned 20 in the late Eighties, the living was easy, with plenty of lucrative student holiday jobs as City messengers or waiters and no shortage of freelance work upon which to build and finance a budding career as an actor, photographer or film director.

But just when it came time to settle down, or to turn those contacts into a serious job with Channel 4, the chill wind began to blow. And when friends who previously could offer a room in a flat began to demand serious rent, where else was there to go but home to Mum and Dad?

In the United States these victims of the recession have been dubbed Ilyas - Incompletely Launched Young Adults. They are the ones who have rushed home at the first sign of trouble because their expectations of what it takes to succeed out there, alone, were formed during the boom years when all the images were of Wunderkinder making it in Hollywood or on Wall Street. These kids feel confused and betrayed that suddenly the streets are no longer paved with gold.

Back home, they can see that their parents' fairly affluent lifestyle has not been too badly hit and cannot fathom why the cuckoo in the nest should not continue to be fed in the manner to which it has become accustomed.

The parents, unsurprisingly, are resentful when friends who come for Sunday lunch are treated to the shameful vision of an unshaven 25-year-old demanding to know why there's not enough milk for his breakfast cereal; or when they discover that the voice of their aspiring television-producer daughter has replaced theirs on the answering machine. They despair at having to revive those awful teenage rows over washing up or borrowing the car.

But worst of all is the secret guilt - especially when they see their contemporaries' children gainfully employed and independent - that this is their fault. They fear it is because they failed to instil any sense of maturity or responsibility into their children that they now expect too much and give up too easily. Remembering the war and the Depression of the Thirties, they wonder just what became of their own parents' lessons of frugality and caution, of hard work and true grit.

Some kids have brought more than their dirty washing home with them. There are also unpaid credit cards, mortgage arrears, failed businesses. 'The worst thing,' says one exasperated father, whose son's restaurant has just closed down, 'is that they're so spineless about everything. He owes a friend of my wife's a fortune for doing the decor, but can't face her and wants his mother to sort things out for him. God only knows how he imagined he could afford to spend so much on fancy paint finishes in the first place.'

This father cares enough about his son not to let him go officially bankrupt, but is angry and bitter that, while the BMW he has always enjoyed driving has had to go to pay his son's debts, as have several items of antique furniture, his son 'still believes he should enjoy pounds 50 haircuts and designer jeans'. The father is too embarrassed to admit to his friends at the golf club the true reason why he has downgraded his car.

One woman, who similarly did not want to be identified - let's call her Mary - belongs to the generation of women who gave up work when they married, but was encouraged by her daughter to think of finding a job once she and her sister had left home. This she did.

The daughter took a degree in modern languages, then started an accountancy course, but felt it wasn't right for her. She decided to retrain as a counsellor, but now, unable to find work, she is back home, demoralised and disillusioned. Her grandmother has just had a slight stroke, but it is Mary who has had to give up her new-found job to look after her mother-in-law.

'I don't know what's happened,' explains Mary, who is utterly bemused at her abrupt return to the caring role. 'We expected them to be so successful. The world seemed to be at their feet. But now she won't even offer to take her grandmother to a hospital appointment. Maybe she has a right to feel cheated, but I don't think I would have met this situation with such . . .' - she pauses to search for the right word, struggling not to be disloyal to her child - '. . . such a poor spirit.'

The feelings of Mary's husband, however, are not so tender. He thinks the best thing they could do for their daughter is chuck her out to fend for herself: Mary has enough to do looking after the older generation without this young adult behaving like a spoilt baby. He and Mary are beginning to have rows about how best to tackle the situation.

'I feel so trapped,' sighs Mary. 'This was supposed to be my little bit of free time. And I feel such a fool complaining to my friends, especially when they're showing me pictures of their grandchildren, that I can't even get my daughter to leave home. I feel as though it's me who has somehow failed to grow up.'

What these opt-out children of the Eighties should beware is not just their parents' exasperation, but the generation that is fast coming up behind them, already honed and toughened by the recession and ready to overtake their scared and cowering older siblings.