China's Foreign Ministry spokeswoman Hua Chunying said on Monday that the use of the United Nations as a platform for a virtual event on the repression of Uyghur Muslims and other minorities in Xinjiang was an insult to the institution.
China has urged U.N. member states not to attend the virtual event, planned by Germany, the United States and Britain.
"The U.S. has banded up with several countries, abused the United Nations' resources and platform, and smeared and attacked China to serve it's own interests," she said at a daily news conference in Beijing.
"This is total blasphemy against the United Nations," she said.
China has said the organisers of the virtual U.N. event, which is due to be held on Wednesday, use "human rights issues as a political tool to interfere in China's internal affairs".
Some Western states and rights groups have accused authorities in Xinjiang of detaining and torturing Uyghurs in camps, which the United States has described as genocide. In January, Washington banned the import of cotton and tomato products from Xinjiang over allegations of forced labour.
Beijing denies the accusations and describes the camps as vocational training centres to combat religious extremism.