Chocolat author Joanne Harris has attacked the “subliminal indoctrination” of children through gendered packaging of books, which she says gives “the false message to a new generation that boys must be clever, brave and strong, while girls should aspire to be decorative”.

Writing in The Author, a quarterly magazine for British writers, Harris described a shelf in her local supermarket stocked with the blue Brilliant Colouring Book for Boys, full of “rocket ships, Vikings, pirates and kites”, and the pink Beautiful Colouring Book for Girls, full of “princesses, puppies, flowers and cupcakes”.

It might appear to adults to be “a harmless marketing strategy”, writes Harris, but for children, who are “highly impressionable”, and for whom “ideas (including prejudices) adopted early on will follow them into adulthood”, it is “really a form of brainwashing, repeating the false message to a new generation that boys must be clever, brave and strong, while girls should aspire to be decorative”, and is “harmful in so many ways”.

The gendering of books is not “limited to children’s fiction”, according to Harris, with a “growing gender division” visible in adult fiction too. As well as the “sea of pastel-pink in the romance section (as if men were neither interested in romance, nor expected to participate in romantic relationships),” the bestselling novelist argues, “there’s an even more worrying tendency among publishers to announce the author’s gender (and thereby the gender of their potential readers) via their book jackets, whatever the content of the book.”

Wartime romances such as Birdsong, The English Patient and Atonement by male authors Sebastian Faulks, Michael Ondaatje and Ian McEwan are given “masculine” covers, says Harris, “featuring soldiers and battlefields”, while “thematically similar” novels The Night Watch, Beloved and Life After Life, by female authors Sarah Waters, Toni Morrison and Kate Atkinson, “have much more conventionally ‘feminine’ jacket designs, featuring women, girls and flowers”.

It’s a divide Harris has struggled with herself, after her publishers proposed a pink jacket design for her novel Gentlemen and Players. According to the novelist, this “rather masculine thriller set in an all-boys’ school” was given a design intended “not to put off your female readers”, but she protested, and found that female readers were not turned away by the lack of pink on the novel’s final cover.

Harris praised the “excellent” group of campaigning parents calling themselves Let Books be Books, who have been pushing for an end to books “for boys” or “for girls” for over a year. Nine publishers have now agreed to “let books be books” and drop gendered labels from their titles for children, but campaigners are continuing to pressure presses including Buster Books, Igloo, and Hodder Children’s Books. The latter publishes Ian Whybrow’s “books for boys” series, described as having “blatant boy appeal, but enough drama, excitement and humour to entice ALL readers”.

“Promoting books for boys is like promoting stereotypes about boys – if you say a book for boys is one about football, what about the boys who don’t like football? These books don’t just exclude girls, they could also exclude boys,” said campaigner Tricia Lowther.

Let Books be Books is also now planning to contact libraries, asking them not to stock gendered books, after hearing from concerned parents about gendered displays in several branches.

“Joanne Harris is exactly right when she writes about children being highly impressionable and that ideas including prejudices can follow them on into adult life. This is one of the reasons we see the Let Toys Be Toys and Let Books Be Books campaigns as crucial to gender equality,” said Lowther this morning.

“If we treat children equally from an early age then they will grow up expecting to be treated equally. Instead we teach them that boys are meant to care about football and dinosaurs (and to turn away from anything ‘girly’), and girls are meant to care about friendship, emotions and looking pretty. Then we wonder why we struggle to get girls to stick with science or sport, why so many men struggle to express their feelings and why women are rated on appearance over ability as they grow up.”