In a 1970s advertisement for Lego, a small girl holds up a free-form construction, made up of a jumble of different types of bricks and figures. She is wearing a blue T-shirt, a pair of jeans and blue sneakers, and her red hair is plaited. The ad features the caption ''What it is is beautiful'', in a call to parents to harness their children's creativity and expression with the endless potential of one of the world's most popular toys.

This old ad hints at exactly what is alarming about Lego's new ''Friends'' range, which was launched in the UK yesterday and will be launched on January 1 in the US to help Lego capture ''the other 50 per cent of the world's children''.

The suggestion from the Danish company is that today's girls are simply not attracted to standard Lego bricks and model sets.

Advertisement: Story continues below Australian commentators Nina Funnell and Dannielle Miller have recently proposed that ''feminine'' toys such as Barbie and Disney Princesses are not harmful to girls because girls can play subversively with them and be taught to think critically. Nevertheless, we ought to ask ourselves why toy aisles are subject to increasing gender segregation. Why must a toy with no obviously gendered connotations, such as Lego, now be manufactured in ''lavender'' with preordained settings such as a hair salon in order for girls to be attracted to it?

What is wrong is not Lego itself, which is responding to perceived market demands and focus groups, but the dramatic change in how consumer goods are marketed to children in the past several decades. The Lego Friends range shows how far we have moved from a world in which a girl might be depicted in marketing materials as ordinary, rather than a tomboy, for wearing practical blue clothing and playing with construction blocks in primary colours.

Lego's market research manager, Hanne Groth, revealed that the company's interviews with young girls showed that their greatest preoccupation was with ''beauty''. This not only meant the visual appeal of toys, which are coded in pastel terms in today's ''pinkified'' girls' culture, but how the girls saw themselves when they projected themselves onto a doll. So while boys might use Lego to build rocket ships or skyscrapers, girls, according to the market research findings, needed specialised figures that would enable them to imagine themselves as beautiful.

We imagine that we have made progress towards gender equality in a country with a woman prime minister, but marketing towards girls and perceptions of what they truly desire have become rapidly more retrograde.

In the 1970s, women entered the work force en masse and the women's liberation movement overthrew the ideal of the pretty, dutiful housewife who encapsulated women's contribution to society. It is no coincidence that there was often less gendering in how toys were presented to children at this time. Even clothing for children was frequently unisex, with overalls and jeans common for boys and girls. Less focus on gender differences in childhood meant greater freedom to explore all aspects of life without being told that boys or girls ''don't do that''.

This is not to deny girls take pleasure in styling Barbie's hair or taking a wavy-haired Lego figurine out on a pony ride. Yet we should be careful to differentiate between innate desires and culturally constructed ones. As Cordelia Fine shows in a study of neuroscientific literature in her book Delusions of Gender, our ideas about ''hard-wired'' differences between boys and girls are baseless.

Such perceptions are based on sexism. The cycle of socialising children into believing that girls should like particular things that boys should not, is not only continuing, but is further compartmentalising children into their genders. This becomes more substantial when these perceptions affect how girls and boys are raised by their parents, making these ''innate'' gender differences a self-fulfilling prophecy.

For instance, Fine shows that girls tend to be silenced and encouraged to be docile more often than boys, and from this we assume boys are naturally louder and boisterous.

Online debate about the new Lego range has questioned why there has been such a focus on what is detrimental for girls to the neglect of the restrictive stereotypes presented to boys.

While the sharply demarcated line between the black, orange and camouflage of the boys' toy section and pink and purple girls' toy section equally critiques boys who stray outside their culturally appointed zone, there is a fundamental difference for girls.

The qualities associated with girls' toys, such as nurturing, are generally seen as inferior to the assertiveness of action figures for boys. Cordoning off particular activities, behaviours and ideas to one gender ignores that there is no justification for doing so and limits the potential of both boys and girls to develop their skills and imagination freely.

If we want to encourage the next generation of children to reach their full potential, whatever their gender, then we need to be able to once again promote the appeal of and ideals behind images like the 1970s Lego girl. She is beautiful without a glittery fairy dress and pastel construction blocks and her mind is free to create and learn without worrying about how she looks.

Dr Michelle Smith is a postdoctoral fellow in the School of Culture and Communication at the University of Melbourne.