The letter, titled "Snickers: Drop Beijing 2022", was addressed to Grant Reid, chief executive of Mars Wrigley - the owners of Snickers.

The American global manufacturer agreed a deal to become the exclusive supplier of chocolates for Beijing 2022 in December 2019 and is one of two non-Chinese sponsors of the Games alongside European brand EF Education First.

"No Beijing 2022" campaigners have applauded Snickers' public commitment to "building strong human rights partnerships" but claim China is "not a viable or qualified candidate for such partnership".

A similar campaign was launched against fellow sponsor Airbnb in January. 

"Snickers should not sidestep those values to reap the financial rewards that come with sponsoring a major sporting event taking place against the backdrop of genocide," read the letter by the coalition of campaign groups.

China has been widely condemned over its treatment of Uyghur Muslims in Xinjiang as well as its crackdown on protesters in Hong Kong and its policies towards Tibet and Taiwan.

A US State Department report published in January accused China of committing genocide against Uighurs and other Muslim ethnic minority groups.

Mandie McKeown, executive director of the International Tibet Network, signed the letter on behalf of the coalition of campaign groups and requested a meeting with Mars Wrigley representatives.

"We urge you to immediately cancel your sponsorship of the Beijing 2022 Olympic Games, or risk being tainted by association," the letter reads.

"By terminating this agreement, Mars Wrigley has an opportunity to send a clear message that it will not tolerate dealing with Governments that profit from occupation, genocide and human rights violations and to make a real difference to the lives of those living under Beijing's tight grip.

"We request the opportunity to meet with you and other representatives of Mars Wrigley to discuss our serious concerns regarding China's attempt to use Beijing 2022 to 'sport wash' the situation facing Tibetan, Uyghur, Hong Kong, Southern Mongolian and Chinese freedom activists."

According to the open letter, the coalition said Snickers failed to respond to a private letter sent more than two months ago.

"Your lack of response only further heightens our fears that your company may knowingly compromise on its public commitments to human rights in exchange for access to the Chinese market," the letter added.

"These concerns are particularly troubling given that Snickers already served as the official sponsors for the 2008 Beijing Summer Games, when China led a brutal human rights crackdown in the lead up to - and during - the Games which was broadcast for the world to see."

In a separate statement, McKeown accused Snickers of "profiting off a regime that is using the Olympic Games to bolster its international reputation and whitewash its brutal crackdown".

"No company should normalise human rights violations of this scale and until Mars Wrigley ends its business relationship with the Chinese authorities, its reputation and commitments will be deeply compromised," said McKeown.

Pema Doma, from Students for a Free Tibet, added: "Mars Wrigley is now faced with a basic choice: it can either do the right thing and terminate its partnership with a Government spearheading one of the world's worst human rights crackdowns in history or pursue a policy of 'business as usual' that will only make the situation worse."

The International Olympic Committee has resisted calls for a boycott of Beijing 2022 after claiming it must stay out of political matters.

insidethegames has contacted Mars Wrigley for comment.