Seven year-old train enthusiast Abbie Rhodes was excitedly looking at train sets online in the hope that she might get one from Father Christmas.

But when she asked her mother, Kim Carnell, to put the "For girls" filter on the Toys R Us website, she was devastated to find that the better, more complicated-looking sets had disappeared from the search listings.

"Why are they saying I can't have that train set because I am a girl?" she asked her mother, before – "losing all confidence in her choices" – she declared she didn't want a train set after all.

Ms Carnell, 34, from Matlock in Derbyshire, wrote to Toys R Us to ask why they used gender filters on their website, saying: "I feel that when a major toy retailer is so openly subjecting our daughters (and sons) to stereotypes this obvious, there really is no hope of these ideas ever being challenged or our children ever reaching their potential outside these stereotypes."

She went on to describe how her daughter, who is also a fan of Frozen and make-up, had been previously bullied at school for liking dinosaurs and for wearing Spider-Man sandals. She felt that this gender separation of toys is "no better than the childhood bullying my daughter has suffered". "It makes me angry and it makes me sad that at seven she feels that there is something wrong with her for saying what she likes," said Ms Carnell, who has two other daughters. "There's nothing wrong with her."

Abbie said that she thinks shops are "being silly and bad" for gender signposting and added: "Toys are for girls and boys and shops should say 'girls and boys' so everyone can play with them, not just some."

Campaigners and politicians have called for shops to stop labelling and segregating toys by gender, with science sets and cars for boys and baby dolls and kitchens for girls, saying it may discourage girls from going into science and engineering.

However, new data released today by the Let Toys Be Toys campaign suggests that retailers are getting the message. Only 50 per cent of major online retailers are now using Boys and Girls signposting on their toy sites compared with 79 per cent of websites reviewed by Let Toys Be Toys in 2012. And none of the online booksellers use gender to organise books.

Jess Day of the Let Toys Be Toys campaign, which was formed in 2012 by a group of parents fed up with the way toys were being marketed, said: "We believe that there is no such thing as a 'girls' toy' or a 'boys' toy'. Marketing toys by gender limits children's choices, limits their chances to learn and develop and it feeds bullying. Selecting toys by gender means that children will only be offered a limited range, and miss out on the chance to find and enjoy things that really interest them."

The study showed that 12 retailers, including Debenhams and John Lewis, still use gender as a prominent way to navigate through product lines. But it pointed out that Tesco and Argos do not use gender but a range of alternative ways to view and sort products such as category, age range and brand.

Interestingly, Amazon does not tend to use gender on its UK site, although gender signposting is prominent in its main US site.

Toys R Us managing director Roger McLaughlan did phone Ms Carnell to discuss this issue and has offered her vouchers to compensate for causing upset.

Last week, Tesco was forced to remove a sign from its stores stating that a superhero alarm clock was a "fun gift for boys' after a picture of a disgruntled-looking Maggie Cole, aged seven, holding the clock went viral.