Debenhams has become the first department store to display size 16 mannequins in its shops, in an effort to reflect the shape of real women in Britain.
The retailer urged rival high street shops to follow its lead as it announced that larger models would be used in its 170 stores around the UK.
The introduction of size 16 mannequins comes just two months after the equalities minister Jo Swinson called for fashion stores to promote a more diverse range of women, saying it was "as if there's only one way of being beautiful".
Nearly all clothes shops in Britain use size 10 or size 8 mannequins, including Topshop and Miss Selfridge, even though the average British woman is a size 16.
Debenhams director Ed Watson said: "The average British woman is a size 16, but the high street has been showing them clothing on a mannequin that is three sizes smaller – until now.
"Having worked on this project for three years, we hope that it will help people in some small way to feel comfortable about their bodies and, crucially, that other retailers will follow."
However, there was a lukewarm response from rival outlets.
A spokeswoman for the British Retail Consortium said it was down to each individual store whether to display plus-size models.
"We won't be issuing guidance in the short term but it's an issue UK retailers take very seriously," she said.
A spokesman for Marks & Spencer said it takes a "responsible approach to visual merchandising" and pointed out that it uses size 10 models, which is above the size 8 market average.
Arcadia Group, the retail giant behind chains including BHS, Dorothy Perkins and Miss Selfridge, did not return a request for a comment.
Swinson said: "Many customers want to see more realistic images in magazines, TV and on the high street, and having mannequins that reflect and celebrate our diverse society is one way of helping to achieve this."
It is not the first time that Debenhams has defied conventional fashion promotion. The department store promoted its Principles range in 2010 with a disabled model, and more recently has banned airbrushing on swimwear advertising and run a lingerie campaign featuring a model over 50.
