A campaign to break down gender divides in children's publishing has met with instant success, after one of the publishers under fire announced they will stop producing titles labelled as "for girls" or "for boys".

The Let Books Be Books campaign, launched this week in time for Saturday's International Women's Day, is the brainchild of the group of parents who have already persuaded retailers such as Toys R Us, Boots and Tesco to market toys in a more inclusive fashion.

Contrasting the predominantly pink covers of books such as The Beautiful Girls' Colouring Book – garlanded with butterflies, cakes and flowers – with the navy-blue The Brilliant Boys' Colouring Book – armoured with axes, helmets and a space-zapper – the campaigners suggest that publishers are sending out "very limiting messages to children about what kinds of things are appropriate for girls or for boys".

'False and stupid assumptions'? ... Buster's colouring books for boys and girls

"People talk about books opening minds and hearts, about them broadening horizons, but these books do the opposite of that," said Tricia Lowther from Let Books Be Books. "Of course there's nothing wrong with boys liking pirates or girls liking princesses, but what about boys who like princesses and girls who like pirates? How will they feel? It's closing down avenues for them finding out who they want to be."

Their petition calling on publishers to "stop labelling books, in the title or on the packaging, as for girls or for boys" gathered almost 2,000 signatures in just one day, amid hundreds of comments from supportive parents.

The former children's laureate Anne Fine, added her voice to the campaign, speaking of how "exasperating" it was that "these false and stupid assumptions about what each gender 'wants' are back in force, narrowing the horizons and possibilities for children of both sexes".

"You'd think this battle would have been won decades ago. But even some seemingly bright and observant adults are buying into it again - quite literally buying into it in the area of 'pink for girls and blue for boys'," said Fine. "There are girls of all sorts, with all interests, and boys of all sorts with all interests. Just meeting a few children should make that obvious enough. But no, these idiotic notions are spouted so often they become a self-fulfilling societal straitjacket from which all our children suffer."

Addressed to children's publishers including Usborne and Buster Books, the petition states that "children's publishing should always aim to open up new worlds for children. But telling children which stories and activities are 'for them' based on their gender closes down whole worlds of interest". It asks publishers to "stop labelling books this way and let children decide for themselves what kinds of stories and activity books they find interesting".

Campaigners have discovered they are pushing at an open door, with Usborne – publisher of a flower-filled, pink Girl's Activity Book and a robot-themed, blue Boys' Activity Book – announcing that a plan to "discontinue publication of titles such as these was decided some time ago". The company takes "feedback on gender-specific titles very seriously", Usborne added, and now has "no plans to produce any titles labelled 'for girls' or 'for boys' in the future".

Lowther declared she was delighted with Usborne's response, and hoped that other publishers would follow.

"It's great that Usborne have agreed to take this step to let children decide for themselves what kinds of stories and activity books they find interesting," she said. "It would be great to know exactly when the current titles will cease to be printed. We look forward to discussing this further with Usborne and supporting them in this decision."

But the campaign has met with stiffer resistance elsewhere. The publisher of The Beautiful Girls' Colouring Book and The Brilliant Boys' Colouring Book, Buster Books owner Michael O'Mara, suggested things were unlikely to change.

"When you have a colouring book which is specifically for a boy or a girl, it sells three times as many copies as one without the sexual categorisation," he said. "These days an awful lot of books are sold on Amazon, and when people search for a present to buy, they'll type in 'present for boy' and will get a whole bunch of books with the word boy in the title. That's one of the main reasons publishers put boy or girl there."

O'Mara could understand campaigners' concerns, he continued, but they would have an "uphill battle" to alter the situation, as "it is so entrenched". Publishers need to "make sure make sure there is no chance of anyone feeling belittled by these sexual categorisations. We certainly don't want to give that idea … It's the colouring book which is brilliant, not the boys."

"We are keeping a very careful eye on that sensitivity, and I accept the complaint that these things can look exclusive, rather than inclusive. But it is not going to disappear. There are boys, and there are girls. [So] while 90% of our books don't have boy or girl in the title … we are going to continue with these categorisations where we think they are necessary, with these sensitivities in mind."

According to campaigners "real children's interests are a lot more diverse, and more interesting" than "robots, space, trucks and pirates" on one hand or a "riot of pink sparkles, fairies, princesses, flowers and butterflies" on the other.

The campaigners' initial target is publishers, but they are then planning to address how booksellers and retailers market books to children. "It would just be nice to see more creativity, and an acknowledgment of the fact that children are happy to have books of stories for children - they don't need separate stories," said Lowther. "The main thing is getting into a dialogue with publishers, like we did with the toys."