US lawmakers are investigating some of the largest clothing companies in the world for using forced labor in their supply chains, potentially violating US trade law.

The House Select Committee on the Chinese Communist Party has written to Temu, Shein, Nike, and Adidas North America, asking about the use of materials and labor sourced from the Xinjiang Uyghur Autonomous region of China.

Any such use would be a violation of the Uyghur Forced Labor Prevention Act of 2021, according to the letters. The Committee has given the companies until 16 May to respond to its questions about suppliers and supply chain policies.

Chinese brands Shein and Temu are also accused of using a 90-year-old loophole to avoid tariffs on goods sold to US consumers.