China's representative said global organisations and media who visited Xinjiang had found the situation was different from its portrayal in the West, and that officials from countries behind the letter declined an invitation to visit.
Britain, France and Germany were among 18 European countries to co-sign the letter expressing concern about "credible reports of arbitrary detention.as well as widespread surveillance and restrictions, particularly targeting Uyghurs and other minorities in Xinjiang".
In the letter, they have urged China to uphold its national laws and global obligations.
China's foreign ministry said the letter "neglected the facts" and was a slander against China, an interference in its affairs and the politicisation of human rights.
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.
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. A United Nations spokeswoman said at the time that the trip, including "full access to Xinjiang", was under discussion.
China says facilities there are "vocational training centres" and they are necessary to fight terrorism and eradicate extremism.
Geng says Xinjiang has not suffered any new violent incidents for more than 2 years.
"We have already lodged stern representations with the relevant countries".
The Chinese government has for decades tried to suppress pro-independence movements among Xinjiang's Muslim community, spurred largely by frustration over the influx of migrants from China's Han majority.
He said the Trump administration's withdrawal from the U.N. Human Rights Council over the panel's criticism of Israel was a "very shortsighted decision".
FILE PHOTO: An ethnic Uighur woman carries a metal rod as she walks down a main road in the city of Urumqi in China's Xinjiang Autonomous Region, July 10, 2019.
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 July 12, the Xinjiang vice-governor responded to global condemnation of state-run detention camps by saying that they were vocational centers which had helped "save" people from extremist influences.