Lego's new Friends line of toys, introduced by the family-owned Danish business in January as a way to target girls, sold twice as many sets than expected, according to the company.

“It has been amazing to experience the enthusiastic welcome that consumers have given the new range. Sales have been quite astonishing,” said Jørgen Vig Knudstorp, the CEO of Lego Group.

But Lego has been criticised for reinforcing gender stereotypes with its Friends packaging and toy design. The range of toys includes 'Stephanie's Cool Convertible' in light purple and 'Mia's Puppy House', which is accessorised with flowers and a pet-grooming kit.

Moving away from the traditional square-set characters, the new, slim figurines have also been criticised by eating disorder specialists.

A petition organised by Spark, a US-based group that campaigns against the sexualisation of girls and young women, called for Lego to change its marketing strategy and has already collected more than 50,000 signatures.

Abi Moore, co-founder of Pink Stinks, a UK campaign group highlighting concerns over the stereotyping of children, told The Guardian that Lego was sustaining a narrow set of ideas.

"We want toys that offer all sorts of opportunities to all children. We think that cupcakes, parties and having everything revolve around leisure is just tiresome and heavily stereotyped,” said Moore.

Last Friday, Lego announced net profits had risen 34 percent, up to 2 billion kroner, in the first half of 2012. Sales increased 24 percent to 9.1 billion kroner, in large part due to the success of the Friends launch.