Publication this autumn of an explicit book for young teenagers about the exploits of a promiscuous young girl has prompted calls for a national ratings system for children's fiction.

The book, Lady, My Life as a Bitch, by the controversial author Melvin Burgess, tells the story of Sandra Francy, who on the eve of her GCSEs, is enjoying sex with a variety of boyfriends until one day she is magically turned into a stray dog.

Set free of guilt by the sudden transformation, she continues to indulge herself with physical pleasures and decides in the end that perhaps it is better to be a 'bitch on heat' than a young woman.

Burgess, the author, first came to notoriety in 1997 with his novel Junk, about heroin use among the young. The book, which was also targeted at younger teenagers, gained a cult following and has been dramatised for both stage and for television. But it also put Burgess at the centre of a nationwide parental campaign for the censorship of young people's fiction.

As early proof copies of Lady begin to circulate this week, the publishing industry is facing demand for a widespread system of categorising contentious books. Already this year a number of the most established names in children's writing have chosen to focus on serious adult political issues.

Beverley Naidoo won the prestigious Carnegie Medal for Children's literature last month with her book The Other Side of Truth, a response to the debate surrounding asylum seekers. The acclaimed writer Michael Morpurgo has also just published Out of the Ashes, his fictionalised treatment of the impact of foot-and-mouth on rural communities.

The publishing trade journal, The Bookseller, has received growing requests in the last few days for children's books to be packaged more carefully, but publishers have so far resisted the idea of adopting a blanket system to deal with problematic material.

'A coloured asterisk on the base of the book's spine,' said Sonia Benster, who runs a children's bookshop in Huddersfield.

'That kind of thing would be useful to parents, booksellers and librarians. The problem with these books is that they quite often end up on the sub-teen shelves.'

Although Benster is more alarmed by violence in teenage fiction than sex, she is sceptical about Burgess's intentions.

'I haven't read this book yet, but it is clearly not the innocent story of a girl changing into a dog. Children are tough little brutes, and not as squeamish as adults, but there should be some guidance.

'I know that Burgess once said he intended to write a book that would do for sex what Junk had done for heroin, so I wonder if he had one eye on the controversy that a book like this would cause. The question is, will a book about teenage sex really have them all up against the walls?'

Burgess denies that the new book has been designed to shock. Although it does depict casual sex as an everyday part of teenage life right from the first pages, he believes that teenagers already know about these issues and appreciate some straight talking.

'As so often with fiction for young adults it comes down to an issue of trust,' he said.

'Young people have access to material far stronger than this all the time, on film, TV, radio, magazines, books - you name it. The only difference with my work is that it tries to speak directly to them about their own lives instead of hypocritically allowing them to overhear, or eavesdrop stuff supposedly aimed at over-18s.'

The book, he adds, was a way of writing about desire and irresponsibility for young adults. 'It's an allegory,' he said.

'Of course teenagers know what kind of context to put Lady in. Even someone who doesn't know what an allegory is will recognise that Lady is not a piece of advice, or a suggestion on how to govern your life.'

Klaus Flugge, publisher of Lady, admits to having had some initial doubts about the book but does not want to see it marked with a warning sticker. 'When I first read the manuscript I was a bit worried,' he said.

'My reaction was that it might encourage children, but I have given it to several booksellers and women to read and they feel it is fun. There will always be some people who will get upset.'

Flugge says he fears the row over the book may start in earnest when it eventually goes into paperback. He regards Burgess as 'our greatest asset' and says the book is aimed at 14 year olds and over. 'Though there will be some children of 12 and 13 who will be advanced enough.'

He also hopes that moves to introduce ratings will not succeed. 'You can do a lot with the cover,' he said.

'This has quite an adult design and is aimed as an adult book as well as a teenage book. I am always against putting warnings or ages on books. But I suppose for some publishers it could be a sales gimmick.'

Caroline Horn, the children's books editor on the Bookseller, is waiting to see if Burgess's new book will force the issue. 'Burgess is very good at throwing things up in the air and this is an issue that needed to be aired,' she said.

'The industry has always veered away from a ratings system simply because of the difficult question of reading ages. One child may be far in advance of another at the same age.'

Lady, My Life as a Bitch may prove a book too far, though, she suspects. Horn points out that many bookshops have separate sections for young adults. 'They are a good idea because many teenagers don't want to go into the children's section, but would feel a little lost in the adult section. I think publishers would find it difficult to agree on a ratings system.'

A spokesman for the Department of Media Culture and Sport said there were no plans to enforce a national ratings system, but the issue was being looked at. The only restraints on publishers are those that come under the Obscene Publications Act.