Top fashion firms pledging to end worker exploitation in their supply chains are hampering progress through irresponsible sourcing practices, according to a report by the Universities of Sheffield and Bath and Royal Holloway under the University of London. It found major brands impose short production windows, cost pressures and constant order fluctuations. These make it difficult for local suppliers to comply with the standards of working conditions that companies including Nike, H&M, Adidas, Primark and Walmart expect.