Anne Fine's adult books put the diss into dysfunction, but as a children's favourite she prefers a gentler touch. Nicholas Tucker asked her about family strife
The line of writers who address themselves to children and to adults is long and growing. Jane Gardam, Penelope Lively and Nina Bawden are respected in both camps, though not Kingsley Amis, who wrote a real stinker for children a few years before his death. This month Anne Fine, whose children's books have won every literary prize going, produces her fourth adult novel, Telling Liddy (Bantam, pounds 15.99). An explosive, mordant account of a grown-up family going wrong, this could be the novel that makes her as celebrated among adult readers as she is with younger ones.

A word about the author before getting on to this self-proclaimed "sour comedy": Fine was born in the Midlands and now lives deep in the Durham countryside. She is 50 but looks younger, cutting a glamorous figure in a profession not always renowned for its dress sense. After teaching briefly and then working as an information officer for Oxfam after university, she married the philosopher Kit Fine in 1968. The relationship eventually terminated having produced two daughters and, in its final throes, a good deal of copy detailing different varieties of marital stress. For the past 14 years, she has lived with Dick Warren, a botanist who specialises in rare orchids.

Quick-tempered and occasionally bossy (traits she is happy to admit to and which often find their way into her female characters), Fine has been a hard-working novelist since 1978. She is essentially a moralist, keen to help children grow in understanding while also richly entertaining them. (Her books are always very funny: one teacher, reading Madame Doubtfire to a class, laughed so much he fell off his chair.)

Telling Liddy concerns four middle-aged sisters whose disastrous falling out reveals the extent of the competitive dislike beneath what appeared to be a closely affectionate extended family. The issue at stake is Liddy's future husband who - rumour has it - once faced a charge of child sexual abuse, which he has stayed silent about ever since. The unknowing Liddy is meanwhile happy to let him bathe and pet her two young children from a former marriage.

Bridie, the social worker sister and the main focus for the story, decides that she must be told. Her other sisters unwillingly agree, only to run for cover when a furious Liddy denounces Bridie as an interfering, jealous bitch and cuts off all contact. Bridie, always more preoccupied with her original family than with her own husband and children, is first bereft and then obsessionally bitter. Betrayed by her other sisters, she vows to betray them in return.

By the end, Bridie's previously rosy image of family life has received a mauling whose ferocity is only equalled in some of Angus Wilson's cruellest short stories. She ceases to be a social worker, no longer believing that any of the other families she has spent so much professional time trying to prop up are worth the effort. Rid of her sisters, she finds more space for herself and her intimates. But by now the damage has gone too far; a final triumphal revenge on the family destroys something in her at the same time. Her patient husband moves out, appalled at the vengeful spirit she has become.

Fine's previous adult novel, In Cold Domain, also featured a dysfunctional family whose grown-up children continued to remain in thrall to their sadistic mother. What has Fine got against the family, the institution that the young characters in her children's books strive so desperately to preserve, despite the worst efforts of their waffling parents?

Her answer is characteristically forthright. "I can never understand those who shake their heads at my novels and wonder whether such disturbed families exist in real life. If you then ask them about their own families, you soon hear about someone who hasn't been spoken to for years or who has behaved disgracefully. Yet people still believe that somewhere out there genuinely happy, positive families remain the rule. Affecting shock at what I write about is too often accompanied by paying lip service to an ideal of family life people know from their own experience to be false."

This type of pessimism does not feature in her children's books. An admittedly protective writer for the young, she makes sure her stories end with the balance between hope and failure at least left even. Although she quotes research suggesting that 78 per cent of second marriages founder over issues arising from stepchildren, she still defends the way that Goggle- Eyes, her wonderful story about the arrival of a new father, ends on a note of cautious optimism. If you can survive the first year of step-parenting, her young heroine advises a school friend just at the beginning of this process, you might all eventually settle down.

Although Fine received numbers of letters from real stepchildren insisting this ending was a cop-out because years after they still hated their own step-parent, she is unrepentant. "I write as a citizen as well as a novelist. Children need some protection from the harshest adult realities."

Even so, her last children's book, The Tulip Touch, hinted at a type of childhood wickedness previously described by writers such as Margaret Atwood, William Trevor and Susan Hill only in novels written for adults. Tulip, the anti-heroine, is an arsonist and would-be child murderess. She is also cruelly treated at home. A dangerous best friend, she soon turns into a pitiless tyrant. Denounced at the end of the story, she refuses to go quietly, staying on in the imagination as our bad conscience about all those children whose suffering we cannot stop but whose subsequent behaviour sometimes proves so disruptive.

But while Fine is a serious novelist, she is never a solemn one. The dialogue in her stories crackles with black humour. A bestseller for children, she proves that quality and success can go together. Nor does she achieve her popularity by low blows, invoking the playground smut or infantile sadism sometimes found in a Roald Dahl story.

Her own childhood, upset at a tender age after coming across Lord Russell of Liverpool's detailed popular study of Nazi atrocities, The Scourge of the Swastika, has remained with her. Occasional moments of blackness in her own books are left to the reader's imagination to flesh out. Those aged around 14 can usually supply the missing details that might, thankfully, still elude the imagination of younger readers.

Her next children's book, The Charm School, will take on various levels of "girlie" behaviour still expected from young females. It sounds like vintage Fine; Bill's New Frock, a previous title, must be one of the best as well as funniest feminist stories of our age. For the moment, Telling Liddy stands as the latest example of Anne Fine's unsettling, unpredictable talent. It is a beautifully written, compulsively readable story from a clever novelist at the height of her powers.