There is a "very credible case" that the Chinese government is carrying out the crime of genocide against the Uighur people, according to a formal legal opinion newly published in the UK.
It concludes there is evidence of state-mandated behaviour showing an intent to destroy the largely Muslim minority in north-western China.
This includes the deliberate infliction of harm on Uighurs in detention, measures to prevent women giving birth - including sterilisation and abortion - and the forcible transfer of Uighur children out of their community.
And, significantly, it says there is a credible case that Chinese President Xi Jinping is himself responsible for these crimes against humanity. It states "the close involvement of Xi Jinping" in the targeting of Uighurs would support a "plausible" case of genocide against him.
It says: "On the basis of the evidence we have seen, this Opinion concludes that there is a very credible case that acts carried out by the Chinese government against the Uighur people in Xinjiang Uighur Autonomous Region amount to crimes against humanity and the crime of genocide."
A legal opinion is the professional judgement of a respected QC - an independent expert in their field - who assesses the evidence and the law and comes to a conclusion. It does not have a legal standing, like a court judgement, but can be used as a basis for legal action.
This opinion was commissioned - but not paid for - by the Global Legal Action Network, a human rights campaign group that focuses on cross-border legal issues, and the World Uighur Congress and the Uighur Human Rights Project.
China's foreign ministry has consistently denied allegations of human rights abuses against the Uighurs in Xinjiang.
The Chinese embassy in London accused anti-China forces in the West of fabricating "lies of the century" about Xinjiang.
The 100-page document - written by senior barristers at Essex Court Chambers in London, including Alison Macdonald QC - is understood to be the first formal legal assessment in the UK of China's activities in Xinjiang.
The opinion is significant because it beats a legal path that British judges would follow if Parliament were to agree new legislation allowing the High Court to decide on matters of genocide. MPs from all parties are hoping to push through this change in the House of Commons on Tuesday, but the government is working hard to avoid defeat.
Ministers are hoping to see off the rebellion by offering to boost the role of parliamentary committees in assessing genocide, but the relevant committees are understood to have rejected the idea.
The legal opinion was based on an exhaustive legal assessment over six months of publicly available evidence from governments, international organisations, academic scholars, charities and the media.
The documents included first-hand witness evidence from survivors, satellite imagery and leaks of Chinese government papers.
The bar for proving genocide is high. A court has to establish acts were committed with intent to destroy, in whole or in part, a national, ethnical, racial or religious group.
In great detail, the opinion sets out evidence of what it describes as the "enslavement, torture, rape, enforced sterilisation and persecution" of the Uighurs.
"There is compelling evidence that detainees are subject to a range of forms of serious physical harm," the opinion says.
"Detainees report having been punished by administration of electric shocks, forced to remain in stress positions for an extended period of time, beaten, deprived of food, shackled and blindfolded."
Measures intended to prevent births within a group are among the activities that count as genocide in international law. The opinion sets out evidence of mass forced sterilisation as part of a plan for population control acknowledged by the Chinese authorities.
It concludes: "There is prolific credible evidence of Uighur women being subject to measures that prevent them from reproducing, either temporarily or permanently (such as by having IUDs non-consensually implanted or through forced removal of their wombs), as well as forced abortions. Such acts would, in our view, clearly constitute a form of genocidal conduct under [international law]."
Genocide can also include the forcible transfer of children from one group to another.
The opinion says: "There is evidence of Uighur children being forcibly removed from their parents. This includes their non-consensual placement in orphanages when one or both parents are in detention, and their mandatory placement in boarding schools.
It continues: "The fact that children are deprived of the opportunity to practise their Uighur culture…, that they are sometimes given Han names, and that they are sometimes subject to adoption by Han ethnic families, all bolsters the evidence that their forced removal is carried out with the intention of destroying the Uighur population as an ethnic group as such."
Significantly, the opinion says there is a "plausible" case that personal responsibility for the genocide lies with President Xi and two senior Chinese officials - Zhu Hailun, deputy secretary of Xinjiang's people's congress, and Chen Quanguo, party secretary in Xinjiang.
It points to leaked internal Communist Party documents, and other evidence, which it says show that "Mr Xi controls the overall direction of state policy and has made a range of speeches exhorting the punitive treatment of the Uighurs. Mr Chen and Mr Zhu have acted upon that overall policy by devising and implementing the measures which have been carried out in XUAR, including mass detention and surveillance."
It says: "We consider that there is a credible case against each of these three individuals for crimes against humanity."
It adds: "The evidence reviewed above suggests the close involvement of Xi Jinping, Chen Quanguo and Zhu Hailun in initiating and implementing a range of measures which, taken together, target Uighurs with a severity and to the extent that one could infer an intent to destroy the group as such.
"In those circumstances, we consider that there is a plausible inference that each of those three individuals possess the necessary intent to destroy, so as to support a case against them of genocide."
The Chinese embassy in London insisted that the population of Uighurs in Xinjiang was growing. All ethnic groups, it said, had the same legal status and freedoms of religion and culture.
"Some anti-China forces in the West have concocted and disseminated plenty of false information about Xinjiang and fabricated "lies of the century" in various forms," the embassy said. "They have smeared China's image and slandered its policies on Xinjiang."
It added: "Anyone who is fair-minded can see that the true intent of those forces is to suppress and contain China's development... Their moves are driven by a Cold War mentality, hegemonic worldview and zero-sum game mindset. China will never allow such farce and vicious demonization to succeed. Lies may mislead people for a while, but cannot win the trust of the world. Facts and truth will eventually bust all lies."