French magistrates have begun investigating claims that four major fashion groups have benefited from forced labour in their supply chains. The multinational companies are accused of using cotton from China's Xinjiang region, where it's believed at least one million Uighur Muslims are being detained and subjected to forced labour. The case is based on allegations by a number of parties, including the human rights and anti-corruption NGO Sherpa. We speak to the group's director Sandra Cossart.