The Thomson Reuters Foundation urged brands from Adidas to Amazon to end sourcing of cotton and clothing from the region and cut ties with any suppliers in China that benefit from the forced labour of the ethnic Uighurs and other Muslim groups.

The Foundation sent emailed questions to more than 30 leading global retailers about their supply chains in China and the origins of the cotton they sourced.

United Nations experts estimate that at least a million Uighurs and other Muslims are held in detention centres in Xinjiang. China has denied mistreatment and said the camps offer vocational training and help to fight terrorism and extremism.

The United States this month hit senior Chinese officials with sanctions over alleged rights abuses against the Uighurs, and Britain and France have recently condemned their treatment.

While most fashion brands do not source from factories in Xinjiang, many of their supply chains are likely to be tainted by cotton picked by Uighurs that is exported across China and used by other suppliers, the rights groups said in a letter.

More than 80 per cent of China’s cotton comes from northwestern Xinjiang, which is home to about 11 million Uighurs.