Rights groups accuse Beijing of abuses against Uyghurs, a mainly Muslim ethnic minority that numbers around 10 million in the western region of Xinjiang, including the mass use of forced labour in internment camps. The United States is among countries who have accused China of genocide.

China has vigorously denied the allegations.

China’s mission in Geneva described the report as a “farce” planned by the United States, Western nations and anti-China forces based on false information and the assumption of guilt.

Speaking ahead of the report’s release, China’s ambassador to the UN in New York, Zhang Jun, said Beijing had repeatedly voiced opposition to it. He said the UN human rights chief should not interfere in China’s internal affairs.

“We all know, so well, that the so-called Xinjiang issue is a completely fabricated lie out of political motivations and its purpose definitely is to undermine China’s stability and to obstruct China’s development,” Zhang told reporters on Wednesday.

“We do not think it will produce any good to anyone, it simply undermines the cooperation between the United Nations and a member state,” he said.

“We have made it very clear to the high commissioner and in a number of other occasions that we are firmly opposed to such a report.”

Bachelet said in recent months that she received pressure from both sides to publish – or not publish – the report and resisted it all, treading a fine line while noting her experience with political squeeze during her two terms as president of Chile.

In June, she said she would not seek a new term as rights chief, and promised the report would be released by her departure date on August 31.

That led to a swell of back-channel campaigns – including letters from civil society, civilians and governments on both sides of the issue. She hinted last week her office might miss her deadline, saying it was “trying” to release it before her exit.

Bachelet had set her sights on Xinjiang upon taking office in September 2018, but Western diplomats voiced concerns in private that over her term, she did not challenge China enough when other rights monitors had cited abuses against Muslim Uyghurs and others in Xinjiang.

In the past five years, the Chinese government’s mass detention campaign in Xinjiang swept an estimated million Uyghurs and other ethnic groups into a network of prisons and camps, which Beijing called “training centres” but former detainees described as brutal detention centres.

Beijing has since closed many of the camps, but hundreds of thousands continue to languish in prison on vague, secret charges.