The business model used by the fashion industry is broken and firms need help to adopt more sustainable practices, MPs have been told.
The warning, from a London College of Fashion academic, comes amid increased scrutiny of the UK's fashion retailers.
Prof Dilys Williams, director of the college's centre for sustainable fashion, said legislation and government support were needed.
Marks & Spencer, Primark, Boohoo and Asos have all given evidence to MPs.
Earlier this month, Prof Williams appeared before the Commons environmental audit committee's inquiry into the sustainability of the fashion industry.
In response to a question from Green MP Caroline Lucas about whether a T-shirt can be produced sustainably for £5.99, Prof Williams said: "If a business is built on fair wages and living within environmental limits then, no, we cannot sell T-shirts at the price that we currently are.
(Former Made in Chelsea star Millie Mackintosh gave items to a pop-up "slow fashion" store in east London-Photo Above)