Best-selling Oxford author Philip Pullman is leading a campaign against the introduction of "repugnant" age bands being placed on the cover of children's books.

From the autumn, many book covers are due to carry a sign stating they are intended for readers aged 5+, 7+, 9+, 11+ and 13+/teen.

But Mr Pullman, who wrote the His Dark Materials trilogy and many other children's books, said he was opposed to the plan because it could deter some readers from picking up his books.

A website has been set up to oppose the guidelines being introduced by leading publishers - and Mr Pullman's name heads the growing list of more than 1,200 authors, booksellers, illustrators, librarians and teachers.

Signatories include Michael Rosen, the Children's Laureate, fellow authors Michael Morpurgo, Jacqueline Wilson and Terry Pratchett - and illustrators Quentin Blake and Shirley Hughes.

Mr Pullman said: "The list seems to be growing all the time.

"Some publishers say this change will help people buy books for children who are not used to buying books, but there are already clues on the bookshelves in the bookshops.

"Putting this guidance on a book's cover seems to suggest it comes with the assent of the author, but that is not the case."

Mr Pullman, who has just returned from a visit to the United States, has asked his publisher Scholastic not to put the age bands on his book covers and the firm has agreed.

In an article in The Guardian, he added: "I know the readers of my most 'difficult' books include people of seven as well as people of 90.

"To write as well as I can, and then find someone at the door turning readers away, is something I find simply repugnant.

"It's based on a one-dimensional view of growth, which regards growing older as moving along a line like a monkey climbing a stick: now you're seven, so you read these books; and now you're nine so you read these."

Mr Pullman composed a statement on the website notoagebanding.org condemning the publishers' plans.

He penned the statement with fellow writers Adele Geras and Anne Fine - and within a day 250 writers had signed up.

The statement said: "We are all agreed the proposal to put an age-guidance figure on books for children is ill-conceived, damaging to the interests of young readers and highly unlikely, despite the claims made by those publishers promoting the scheme, to make the slightest difference to sales.

"We take this step to disavow publicly any connection with such age-guidance figures, and to state our passionately-held conviction that everything about a book should seek to welcome readers in and not keep them out."

Joel Rickett, deputy editor of The Bookseller, said: "The steps taken by Mr Pullman and other authors have taken the industry by surprise and I think these proposals are now in the balance.

"Publishers thought the banding would give people a clearer sense of which book to match with which child.

"There is a huge and diverse output in children's books, which can be confusing for the non-expert. But if the top swathe of children's authors say they do not want it, then it might not go ahead."