Rubio is chairman of the Senate Foreign Relations subcommittee that oversees human rights, and McGovern chairs the Congressional-Executive Commission on China.

The letters were sent to the chief executives of the companies, who were asked to respond to questions about their exports to China.

The executives were asked whether they knew their technology would be used to support surveillance activities conducted by China’s police forces and whether they took steps to ensure their products were not used for human rights abuses or to compromise US national security.

Nvidia is saying nothing and Intel spokesman William Moss said the company does not tolerate its products being used to violate human rights and when the company becomes aware of such a concern it ceases or restricts business with third parties until it has confidence its products are not used to commit such violations.

The United Nations has estimated that more than a million Muslims have been detained in camps in the Xinjiang region. The US State Department has accused Chinese officials of subjecting Uighur Muslims to torture, abuse “and trying to basically erase their culture and their religion”.

China denies mistreatment and has said the camps provide vocational training and are needed to fight extremism.