Christian Solidarity Worldwide (CSW) has launched a letter-writing campaign asking Marks & Spencer to reassure shoppers that it does not use Uighur slave labour in the manufacture of its clothing.
Marks & Spencer is one of the many fashion retailers and apparel brands recently accused by human rights groups of using supply chains "tainted by Uighur forced labour". Others include Calvin Klein, Zara, Adidas, Gap, H&M, Muji, Polo Ralph Lauren and Tommy Hilfiger.
The plight of China's persecuted Uighur Muslims has gained increasing international attention in recent months after drone footage showed blindfolded and shackled Uighur men being boarded onto a train.
It is estimated that over a million Uighurs are in re-education camps in Xinjiang Uighur Autonomous Region. British MPs have accused China of a "systematic and calculated programme of ethnic cleansing" against them.
CSW said many Uighur prisoners are sent to clothing factories that supply Western brands.
It is asking Marks & Spencer to confirm that it is not supporting or benefiting from the enforced labour of Uighurs.
The letter quotes one Kazakh woman who was freed from an internment camp only to be sent as forced labour to a clothing factory.
"The clothes factory was no different from the [internment] camp. There were police, cameras, you couldn't go anywhere," she said.
The letter urges Marks & Spencer to cut ties with factories implicated in forced labour and to refuse to source cotton, yarn, textiles and finished products from the Uighur region.
"The entire clothing industry is potentially tainted by forced Uyghur labour, and credible reports have implicated dozens of brands – including M&S," it reads.
"The onus is on each corporation, including M&S, to make a clear statement and ensure that it is not part of the problem."
Marks & Spencer did not respond to a request for comment.