Boris Johnson has rejected calls to boycott the 2022 Winter Olympics over China’s treatment of the Uighur people.
At Prime Minister’s Questions, Lib Dem leader Sir Ed Davey said genocide was “happening in front of our eyes”.
Mr Johnson said the UK was “leading international action in the UN to hold China to account”.
But he rejected Sir Ed’s call for Team GB to stay away from the Beijing games, saying the UK did not “normally” support sporting boycotts.
In October, Foreign Secretary Dominic Raab suggested the UK could make an exception to this rule, given the scale of the human rights abuses in China’s Xinjiang province.
Sir Ed Davey has written to the heads of the British Olympic Association and the British Paralympic Association calling on them to withdraw their athletes, unless China closes detention camps in Xinjiang and ends the “ethnic cleansing of Uighurs”.
He also calls for the end of Uighur forced labour, torture, sexual assault and other human rights abuses.
In the letter, seen by the BBC’s Sports Editor Dan Roan, Sir Ed says: “The teams you send are the nation’s best athletes and under no circumstances should we allow them to be used as propaganda for the Chinese Communist Party given what we know is occurring in Xinjiang.”
If British athletes are sent to the games, he adds, they should “not be gagged from speaking out against the Chinese regime”, despite International Olympic Committee (IOC) rules preventing athletes from protesting at Olympic venues.
China has consistently denied allegations of human rights abuses against the Uighurs – a Muslim minority group which lives mostly in the Xinjiang region – insisting camps there were “vocational educational and training centres”.
But more than 180 organisations have called on governments to boycott Beijing 2022, which the World Uyghur Congress described has described as “a genocide Olympics”.
Dorjee Tseten of Students for a Free Tibet, one of the groups that signed the letter, told the BBC: “It is unfortunate that history is repeating what happened 82 years ago with the Nazi Olympics in 1936.”
IOC vice president Dick Pound said earlier this month that barring athletes from participating in the event would be “a gesture that we know will have no impact whatsoever”.
Raising the issue in the House of Commons, Sir Ed said: “Today millions of Uighur people in China live in fear under a cruel regime.
“The BBC, international media and human rights NGOs are all reporting on forced labour camps, women being raped and sterilised and families being separated. This is a genocide happening in front of our eyes.”
Mr Johnson said Sir Ed was “right to highlight the appalling campaign against the Uighurs in Xinjiang”.
“That’s why the foreign secretary has set out the policies that he has, the package of measures to ensure that no British companies are complicit in or profiting from violations,” he added.
“We’re leading international action in the UN to hold China to account and will continue to work with the US friends and partners around the world to do just that.”
But he added: “We’re not normally in favour of sporting boycotts in this country and that’s been the long-standing position of this government.”