Britain on Sunday accused Beijing of "gross, egregious human rights abuses" over its "deeply troubling" treatment of ethnic and religious minorities in China's western Xinjiang region.
Rights groups and experts estimate that more than one million ethnic Uighurs and other Turkic-speaking minorities have been rounded up into a network of internment camps.
British Foreign Secretary Dominic Raab said the reports of forced sterilisations and mass detentions in the predominantly Muslim region required international attention.
"It is clear that there are gross, egregious human rights abuses going on... it is deeply, deeply troubling," he told the BBC.
"The reports and the human aspects of it... are reminiscent of something we have not seen for a long, long time, and this is from a leading member of the international community that wants to be taken seriously.
"We want a positive relationship (with China), but we cannot see behaviour like that and not call it out," Raab added.
His comments come as tensions between London and China are rising over a host of issues.
Britain on Tuesday bowed to sustained pressure from Washington and ordered the phased removal of Chinese telecoms giant Huawei from its 5G network despite warnings of retaliation from Beijing.
The two sides have also clashed over Beijing's imposition of a controversial national security law in Hong Kong.
- 'Resolute response' -
The United States earlier this month slapped sanctions on senior Chinese officials, as it demanded an end to the "horrific" abuses against Uighurs and other Turkic Muslims in Xinjiang.
Beijing swiftly responded with counter measures in one of the latest episodes in deteriorating US-China relations.
Raab said he will update British lawmakers on Monday on the UK government's next steps regarding Beijing's draconian new law in Hong Kong.
That will include announcing the outcome of a review of extradition arrangements with the former colonial territory.
However, China's ambassador to London warned Sunday that it will make a "resolute response" if Britain follows the US in sanctioning Chinese officials for the alleged abuses.
"We never believe in unilateral sanctions, we believe the UN (United Nations) has the authority to impose sanctions," Liu Xiaoming told the BBC.
"If the UK government goes that far to impose sanctions on any individuals in China, China will certainly make resolute response to it."
Liu said he did not want to see "tit-for-tat" diplomatic skirmishes between Britain and Beijing, as was happening with the US.
"I think (the) UK should have its own independent foreign policy rather than dance to the tune of the Americans like what happened to Huawei," he added.