But the camps form “only one piece of the whole puzzle”, said US-based scholar Adrian Zenz, who told lawmakers on Thursday that Beijing was simultaneously pursuing a strategy “to place the vast majority of minority adults into different forms of coercive or at least involuntary labour”.

Testifying before legislators on the Congressional-Executive Commission on China (CECC), Zenz said that camp detainees were being put to work in factory jobs located in or near to camp compounds in a “grand scheme” of coercive labour.

The employing companies would receive government subsidies of up to 6,800 yuan (US$961) for each individual trained and employed, as well as a shipping cost subsidy of 4 per cent of their sales volume, said Zenz, whose research is based largely on public records, often originating from the government itself.

Cheap minority labour combined with state subsidies meant that companies would be able to undercut global prices and “turn ‘made-in-Xinjiang’ into a multibillion-dollar business model”, said the scholar.

A report by the Centre for Strategic and International Studies (CSIS) released on Thursday, based on an examination of public research and interviews with former detainees, found that apparel was the primary sector affected, and identified the US as a major recipient of such exports.

Cotton production in Xinjiang forms around 84 per cent of nationwide production of the crop, while US imports of Chinese apparel take up over 30 per cent of the American market, the report noted. And while only a small fraction of imports to the US arrived directly from Xinjiang, many other products may contain textiles “tainted by Xinjiang’s forced labour”.

Growing scrutiny over allegations of forced labour in Xinjiang has already caused some multinational companies to sever links with suppliers in the region.

On Wednesday, ABC News in Australia reported that two retailers, Target Australia and Cotton On, had stopped buying cotton from their Xinjiang-based suppliers following their own internal investigations into their supply chains.

And earlier this month, citing concerns over forced labour, US Customs and Border Protection (CBP) issued an order to halt all imports of garments from one Xinjiang-based clothing manufacturer.

US to raise human rights issues in Muslim-heavy Chinese region at UN

The company, Hetian Taida Apparel, supplied pyjamas to wholesale retailer Costco and shipped over 135 tonnes of clothing to the US in 2018, according to figures from Panjiva, a global supply chain tracker.

In a statement on Thursday, the American Apparel and Footwear Association (AAFA) said it was “deeply concerned” by reports of forced labour within the supply chains of US companies, and called on the Chinese government to “facilitate all due diligence measures to assure a clear understanding of the facts”.

“We have been working closely with our members to educate them with available information about labour practices in Xinjiang province,” said the AAFA, which represents over 1,000 companies.

Experts told lawmakers on Thursday that the burden of proof should be shifted to companies to confirm that their products were not made by those working against their will, but warned that due diligence was difficult given the limited access that authorities in Xinjiang give to outside officials or inspection teams.

Pompeo accuses China of ‘enormous rights violations’ in Xinjiang

In light of recent “potemkin” tours for foreign journalists and officials in Xinjiang, where access is closely controlled, “it is inconceivable that any worker would tell the true side of the story”, said Nury Turkel, chair of the Washington-based Uygur Human Rights Project (UHRP).

Lawmakers are currently considering whether to introduce new legislation focused specifically on a policy response to the forced labour issue in Xinjiang, according to multiple sources with knowledge of the deliberations.

One State Department official said that absent of new legislation, the onus was on the White House to take executive action.

“If [US President Donald Trump] wanted to show leadership, he could make an executive order that he signed declaring that if Xinjiang is going to be a forced labour zone, it should not be trading with the rest of the world,” said a State Department official, speaking on condition of anonymity.

“If we had a normal president, it’s not that hard and we could do this overnight,” the official said.

UN chief rejects claim he did not condemn China over Xinjiang Muslims

Last week, the departments of State and Commerce unveiled a suite of sanctions targeting Chinese officials, government bodies and private companies over their involvement in Beijing’s mass internment and surveillance programmes in China’s far west.

Action taken by the State Department to deny US visas to Chinese officials deemed responsible for or complicit in Beijing’s “campaign of repression in Xinjiang”, was applauded by human rights advocates, but was enacted outside the Global Magnitsky Act, which would publicly identify the individuals and also subject them to economic sanctions.

“We need to name names,” Michael Posner, who served as assistant secretary of state for democracy, human rights and labour under Barack Obama, told lawmakers on Thursday.

Welcoming the administration’s recent action, Posner, now director of New York University’s centre for business and human rights, said that the impact of such moves was nonetheless undermined by US President Donald Trump’s silence on Xinjiang.

“The commander-in-chief is the primary spokesperson for the United States,” said Posner. “And if he’s not echoing or even leading in the same direction as Secretary [of State Mike] Pompeo … it allows somebody like Xi Jinping to say ‘I’ll listen to the guy I’m talking to – the president – and I can ignore the rest’.”