The candid novels of Judy Blume have been devoured by teenagers for 20 years. And her capacity to shock their parents still frankly astonishes her, she tells Glenda Cooper
My first encounter with Judy Blume was furtive, embarrassed and confused. I was 12 when I read her book Forever, which graphically describes a teenage girl's first love affair and experience of sex. Our school banned it, immediately ensuring that the whole of the first year read it, passing the dog-eared, scruffy copy under desk lid to desk lid.

For anyone who did not grow up in the 1970s or does not have teenage daughters, Judy Blume's name may not be immediately familiar. Yet her books still regularly appear on children's best-seller lists and she is always voted one of the most popular authors by children. In the UK alone she has sold 700,000 books. Are You There God? It's Me Margaret, Blume's first commercial success and her top seller in the UK, dealt with a young girl trying to resolve religious dilemmas while at the same time praying that her mother would let her buy a bra. It's Not The End of the World details a young girl's futile efforts to reunite divorcing parents. The narrator in Then Again Maybe I Won't has wet dreams and worries about his parents seeing the bedsheets.

David Fickling, the publishing director of Scholastic Children's Books, describes Blume's novels as a "wonderful corrective to the rather over- literary children's books which were around in the 1970s. Everyone got offended and no one had read anything nearly as shocking. It was deeply needed. She spoke directly to kids in an emotional way, and of course it was deeply attractive because it was from America and to teenagers everything from the States is more sexy."

But in the world of television programmes such as Byker Grove and explicit magazines like Bliss, Sugar and More!, are Judy Blume's books really as relevant as they once were?

Certainly, Forever is still making waves. It was this book that really made Judy Blume's name, with its painfully honest descriptions of Karen's first experience of sex with her boyfriend Michael and his penis nicknamed Ralph. [No teenage girl I knew could meet a boy called Ralph again for years without sniggering.]

"Oh Forever," says Blume, who is in Britain to take part in a sponsored reading event for children's charities. "I can't believe I'm still talking about this book 20 years later. The American Libraries Association has just given me an award after all these years with a specific citation for Forever. I've said before I don't want any awards because that would mean that they approve of me and therefore the kids won't like me." She looks conspiratorially at me. Elfin, looking far less than her 58 years, she draws you into the sort of intense conversations that you had as a 12-year-old when it was the end of the world if the object of your desires in the fifth form wouldn't look at you.

She still has plenty of readers. They write avidly - she receives more than 200 letters a week - requesting bust-development exercises and more details on sex. Another said: "How can I tell my mother that I know some things about sex?" One more simply said: "I am desperate."

"I don't think the basic characters or things I write about have changed over 20 years," said Blume. "It's always families, friendships and schools. And I think that except for the fact children have had more limited experiences than adults their feelings aren't any different."

She is amazed when people criticise her for tackling difficult subjects: "I don't know why adults think children are not interested in those things. I have a five-year-old grandson and I know what his feelings are and his concerns are. He may pick up the phone and tell me what Lego set he wants for his birthday but I have also heard him say "My mum and dad are separate" and it just broke my heart..." She breaks off in tears. "They're divorced and I know that is what is on his mind at the age of five."

Blume started writing during her first marriage, which itself ended in divorce. "I had had two babies by the time I was 25. I married when I was in college because we all did that then. That was great fun but the creative outlet I had all the time I was in school I missed to the point where my health was affected. I was not happy. Writing saved my life, my physical health and my mental health."

Yes, she admits that her own life influenced her work - her novel Starring Sally J Freedman as Herself is her most closely autobiographical - but she says she has moved beyond this: "When I give talks to kids I explain about my family. I show them a picture of my older brother and say 'think about brothers in my books'. And when I show them a picture of my parents maybe they can understand why I've written often about very nurturing fathers, close relationships between daughters and fathers, because that's what I had, and more remote, worrying, over-protective mothers."

As for what her daughter and son - now in their mid-thirties - think of her books, she refuses to say: "I don't think they thought very much about it at all. I don't think they think much about it at all that now. They don't see me as a writer but as their mother. My daughter Randy will say, 'For someone who can never find her keys or glasses I don't know how you manage to organise yourself to write books'."

She remains passionate about a child's right to information: "Why did they take the books out of your school all those years ago?" she asks me. "Because they didn't want to answer your questions or deal with the questions of your sexuality or puberty at all. They think 'we won't talk about it so it won't happen'. And then kids aren't prepared."

Although her books seemed shocking when Blume began writing, she feels there was a far freer atmosphere than there is now, at least in the US. "We didn't have the Moral Right in the 1970s when I started. That came in after the 1980 election and it's been with us now for 15 years, I'm sorry to say."

In that time her books have been banned from libraries and schools because of their supposedly explicit nature. "But I do think people are fighting back now. At first it was like, 'Oh please, this is America', and they didn't pay careful attention to what was going on. The publishers, the libraries and teachers were caught out because they weren't prepared.

"Now all libraries are told to have policies in place. Parents can't just frighten a teacher or a librarian in the way they used to, when they could come into school waving any old book that they hadn't even read in the first place."

Blume herself is a spokesperson for the National Coalition Against Censorship, something she takes very seriously. "Teachers I know have had their houses firebombed and have been physically threatened because of books they let their class read. But I am more optimistic now than if you had asked me five years ago. Much more. People are now saying to the moral right 'You can choose what is right for your children but not for all children'. We are seeing people who are fed up with Newt Gingrich and Pat Buchanan who are always telling us 'danger danger danger scare scare scare children children children'. Family values has now become this crazy codeword. I mean we all have family values. I have a family. My family has values. Gingrich and Buchanan - they don't own family values."

For Blume herself, she says she will carry on writing exactly as she always has: "I don't see anything controversial about puberty. I still don't; I never have. It's an exciting part of life and kids are curious about it, but it is not sensational."

Does she feel, like many other successful writers for children, that she never wanted to grow up? She shivers: "I wouldn't want to be a teenager. I wouldn't want to go back to 1956 and I wouldn't like to be a teenager in 1996. Once you get through the teenager years I don't know anyone who wants to go back. It's so tough".