A Uyghur rights group told a London court on Tuesday that the British government has unlawfully failed to investigate the importation of cotton produced with “slave labour” in the Chinese province of Xinjiang.

The World Uyghur Congress (WUC), an international organisation of exiled Uyghur groups, is taking legal action at London’s High Court against the state’s Home Office, HM Revenue and Customs (HMRC) and National Crime Agency (NCA).

Its lawyers say the Home Office has wrongly refused to launch a probe into the importation of foreign prison-made goods, and that HMRC and the NCA have failed to investigate whether cotton from Xinjiang amounts to “criminal property”.

Jenni Richards, representing the WUC, told the court that approximately 85 percent of Chinese cotton comes from Xinjiang and that “putting internment camp detainees to work in factories is a Xinjiang-wide policy”.

Rights groups accuse Beijing of widespread abuses of Uyghurs, a mainly Muslim ethnic minority that numbers around 10 million in the western region of Xinjiang, including the mass use of forced labour in camps. Beijing vigorously denies any abuses.

Lawyers acting for Britain’s Home Office, the NCA and HMRC told the court that there has to be a clear link between “the alleged criminality and its specific product” to investigate whether goods are made in a foreign prison.

James Eadie, representing the three defendants, also argued in court filings that the WUC has not provided any evidence of identifiable criminal property, but that the NCA “may commence an investigation” if there is sufficient evidence.

The WUC’s UK director Rahima Mahmut told Reuters outside court that she has not seen her family in Xinjiang for almost six years, saying: “I don’t know what happened to them.”

She added: “Although the UK Government has been very, very strong in words condemning China … there is no meaningful action.”

The WUC’s case comes amid global efforts to stop the importation of products allegedly made with forced labour that originate in Xinjiang, following reports of alleged human rights abuses by China against Uyghurs and other Muslims in the region.

Draft rules drawn up by EU lawmakers would ban any products “for which forced labour has been used at any stage of their production, manufacture, harvest and extraction”, while the United States last year enacted the Uyghur Forced Labour Prevention Act.