China and the International Olympic Committee (IOC) have faced a deluge of criticism ahead of the Games over the host nation's human rights record.

There has been widespread condemnation of Beijing's treatment of Uyghur Muslims in Xinjiang as well as its crackdown on protesters in Hong Kong and its policies towards Tibet and Taiwan.

The letter has been sent almost a year to the day before the Winter Olympic Opening Ceremony is due to be held in Beijing on February 4 next year.

Signatories said they were now targeting Governments and world leaders as the IOC had "completely failed" to take any action "despite clear evidence of genocide and widespread and worsening human rights failures".

"It now falls on Governments to take a stand and demonstrate that they have the political will to push back against China's reprehensible human rights abuses," a statement said.

The letter claims that Beijing's hosting of the Summer Olympic Games in 2008 merely "emboldened the Chinese Government's actions" and led to "a gross increase of the assault on communities living under its rule".

But the IOC has repeatedly insisted that it must remain "neutral" on political issues and China has rejected the international criticism, claiming instead that its human rights situation is improving and firing back at what it sees as foreign meddling. 

Beijing has also claimed that camps in Xinjiang, where more than a million Uyghur people are believed to be held, are in fact schools designed to combat extremism.

The signatories of the letter have pledged a global campaign in the year leading up to the Olympic Opening Ceremony.

"The Winter Games 2022 being awarded to China was a slap on the face of every Uyghur, Tibetan, Southern Mongolian, Hong Konger, Taiwanese and Chinese democracy activists," said Zumretay Arkin of the World Uyghur Congress. 

"Our sufferings were completely dismissed by the IOC. 

"It's now up to the Governments to act on it, and show some decent humanity by boycotting a genocide Olympics."

John Jones, of Free Tibet, added: "The IOC's ongoing insistence that the 2022 Winter Games take place in Beijing, a city from which the Chinese Communist Party is directing genocide, brutal security crackdowns and cultural destruction, becomes more absurd and vicious every day. 

"No lessons have been learned from 2008 and horrific new mistakes are being made. 

"The only way we can begin to remove this stain on our collective conscience is for Governments to carry out a diplomatic boycott."

An Inter-Parliamentary Alliance on China, which includes politicians from the United States, Britain, Japan, Australia and the European Union, has previously put pressure on the IOC.

Campaigners have also started to target Olympic sponsors with Airbnb urged to withdraw its backing of Beijing 2022 last month.

Chinese President Xi Jinping and IOC counterpart Thomas Bach had a telephone call about preparations on January 25, however, as work to stage the Games pushes ahead.

"Awarding the Olympic Games to a National Olympic Committee does not mean that the IOC agrees with the political structure, social circumstances or human rights standards in its country," an IOC spokesman told insidethegames last year.

"Given the diverse participation in the Olympic Games, the IOC must remain neutral on all global political issues."