"What we have here is human rights abuses and that's why Michelle Bachelet needs to be able to go there with her team of experts on terms that she considers acceptable so that they can make a credible and independent evaluation of what's going on", he said.
According to the U.N., the United States, and independent assessments, China has forced between almost one and two million Muslim minorities into the detention facilities, known as mind-transformation or re-education camps.
"We call on China to uphold its national laws and worldwide obligations and to respect human rights and fundamental freedoms, including freedom of religion or belief in Xinjiang and across China", the letter said.More news: Apple looks to make India its export hub
The ambassadors chose to raise their concerns in a letter instead of a resolution, which China would have undoubtedly squelched.
China says the camps are "training centers" to equip people with employable skills to help combat Islamist extremism in Xinjiang province, still the site of frequent violence.
Diplomats rarely send open letters to the 47-member council to criticize a country's record, but the move may have been the only available option to spotlight Xinjiang, with China likely having enough support to vote down a formal resolution.
China has attacked a statement by 22 Western countries, including Switzerland, at the United Nations urging it to stop holding members of its Muslim population in detention centres, calling the measure necessary for national security and accusing the countries of trampling on its sovereignty.
FILE PHOTO: People hold signs protesting China's treatment of Uighur people in the Xinjiang region, in Vancouver, British Columbia, Canada, May 8, 2019.More news: Melvin Gordon to hold out, request trade unless given new deal
Charbonnau also said he hoped the United States, which has been very outspoken about alleged Chinese human rights violations, would "swallow its pride" and sign the letter.
No Western delegation was willing to take the lead and expose itself as a "ringleader" through a joint statement or resolution, diplomats said.
At the start of the three-week session, which ends on Friday, the Xinjiang vice governor responded to the global condemnation of the state-run detention camps by saying that they were vocational centres which had helped "save" people from "extremist" influences.
China had now effectively contained "terrorism" and "religious extremism" in Xinjiang, Vice Governor Erkin Tuniyaz told the council in an appearance that was sharply criticised by the US.More news: Ariana Grande Talks All-Consuming Grief Over Mac Miller
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