Jemma Moonie-Dalton, from London, said she was “dismayed” by the choice of school shoes for her seven-year-old daughter.
“In the boys’ section the shoes are sturdy, comfortable and weather-proof with soles clearly designed with running and climbing in mind,” she wrote on Facebook to Clarks on 8 August.
“In contrast, the girls’ shoes have inferior soles, are not fully covered and are not well-padded at the ankle. They are not comfortable and are not suited to outdoor activities in British weather.”
Moonie-Dalton continued: “What messages are you giving to my daughter? That she doesn’t deserve shoes that put her on equal ‘footing’ with her male peers?
“That she should be satisfied with looking stylish whilst the boys are free to play and achieve in comfort?
“That she shouldn’t try and compete with boys when they play chase – girls’ shoes aren’t made for speed, so perhaps girls aren’t either?
“These messages may not be explicit, but they are there, and are insidious.”
The mum said she was “deeply angered” by Clarks’ “persistent discrimination”.
Writing openly to the retailer, she continued: “As market leaders you have an opportunity to lead the way by designing and marketing shoes for 21st century children.
“I look forward to your detailed consideration of my letter, and until I hear a satisfactory response I will be sharing my concerns with a wide audience.”
The Facebook post had more than 33,000 likes and 13,000 shares, and it received nearly 6,000 comments in less than two days.
Speaking to HuffPost UK, a spokesperson for Clarks said: “Clarks has a gender-neutral ethos that anyone can choose any style they would like.
“Over the past few seasons, following customer feedback and market research, we have focused on creating more unisex shoes and we are looking at a number of elements of our business to promote this gender neutral ethos, both on our website and within our stores.
“As a large global company, it is not always possible to implement all the changes we want to make as quickly as we would like.
“However, we are looking to move as fast as we can to ensure this ethos is reflected throughout our brand.
“Today we have more unisex styles in our range than ever before.
“This means we now have a wider range of closed-in styles, school boots and Gore-Tex styles and these changes will continue in our Spring/Summer 2018 range, which has been designed with an entirely unisex approach.
“In addition, in September we will roll out a new format in some of our stores, where the whole kids department will be unisex with shoes displayed by ‘story’, rather than gender.”