The Royal Family and UK ministers are being urged to boycott the 2022 Beijing Winter Olympics over alleged human rights abuses.
Labour says the measure is necessary unless China allows the UN to carry out a thorough investigation into “systematic persecution” of Uighur Muslims.
Beijing has rebuffed international claims about the alleged atrocities in Xinjiang province.
But more than a million people are said to have been arbitrarily detained – amid claims some have been subjected to torture and forced sterilisation.
Foreign Secretary Dominic Raab and Culture Secretary, Oliver Dowden, have both been pressed to announce a political boycott.
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Mr Raab announced in March how four Chinese officials would be sanctioned over “appalling violations” of human rights against Uighur Muslims in Xinjiang.
The foreign secretary described the atrocities as “one of the worst human rights crises of our time”.
And he warned how the world “cannot simply look the other way”.
Shadow foreign secretary, Lisa Nandy, and shadow culture secretary, Jo Stevens, wrote to their government counterparts asking them to demand “unfettered access” for the UN to conduct a “full, transparent and independent” probe.
“We have consistently pressed the government for more robust actions to address this appalling situation, including more extensive sanctions against senior officials responsible for what is taking place in Xinjiang and more robust measures against forced labour,” the Labour MPs said.
“We are now calling on you to use the occasion of the Games to press the case for unfettered UN access to Xinjiang to conduct a full, transparent and independent investigation.
“This has been repeatedly sought by the UK and other governments but has not yet been realised.
“If this is not granted, the UK government should not send ministers, Royal Family members or senior representatives to participate in any official duties or ceremonies at the Beijing Olympics.
“The Chinese government will want the Games to be a diplomatic success.
“A political boycott by the UK and other states would send a strong signal of the deep global concern with the plight of the Uighur and prevent the Games being a PR exercise for the Chinese authorities.”
The political boycott should be triggered if China does not grant inspectors access to Xinjiang by 14 September – the opening of the UN General Assembly session in New York.
Ms Nandy said: “For as long as China continues to block access to Xinjiang, no self-respecting government should even consider handing a PR coup to Beijing.
“The UK parliament recently took the unprecedented step of recognising what is happening to the Uighur is genocide.
“After a decade of Tory prime ministers rolling out the red carpet to Beijing, this must be the turning point.”
But Labour has stopped short of calling for a sporting boycott, suggesting it would be unfair on both competitors who have trained for four years and the Chinese people, who are not responsible for the situation.