Senior Tories have expressed anger at the decision to invite Chinese leaders to the Queen's state funeral on Monday.
In a letter to the Commons and Lords Speakers, a group of MPs and peers said it was "extraordinary that the architects of genocide" against Uighur Muslims had been asked to attend.
Some 500 foreign leaders are expected to be at the funeral but invitations have not been extended to Russia and Belarus after diplomatic relations broke down over the war in Ukraine.
Myanmar has also been excluded as its Government took power through a military coup. It is understood that some countries, including Iran, will only be represented at an ambassadorial level.
Tory MPs Sir Iain Duncan Smith and Tim Loughton - who were among the politicians sanctioned by Beijing for speaking out over the treatment of Uighur Muslims in Xinjiang province - sounded the alarm over the decision to invite China to the state funeral.
The letter, also signed by crossbench peer Lord Alton and Labour peer Baroness Kennedy, said: "We are greatly concerned to hear that the Government of China has been invited to attend the state funeral next week, despite other countries Russia, Belarus and Myanmar being excluded.
"Given that the United Kingdom Parliament has voted to recognise the genocide committed by the Chinese Government against the Uyghur people it is extraordinary that the architects of that genocide should be treated in any more favourable way than those countries who have been barred."
Vice President Wang Qishan is expected to attend the funeral on Monday in Westminster Abbey, according to the South China Morning Post.
It is unclear whether President Xi Jinping will attend. He is currently meeting Russian president Vladimir Putin at a summit in Uzbekistan.
The parliamentarians said it was inappropriate to allow the Chinese delegation access to the Palace of Westminster, where the Queen is lying in state until the funeral.
The Chinese ambassador to the UK Zheng Zeguang was barred from Parliament last year.
The letter said: "It is also particularly inappropriate given that seven parliamentarians including ourselves remain sanctioned by the Chinese Government and you along with the Lords Speaker have quite rightly barred the Chinese Ambassador from attending the Palace of Westminster whilst these unjustified sanctions remain in place.
"It may well be as part of the arrangements for foreign dignitaries attending the state funeral that facilities at the Palace of Westminster will be made available to them before or after attending the service at Westminster Abbey.
"I am sure you will agree that it would be wholly inappropriate that any representative of the Chinese Government should be able to come to the Palace of Westminster and that you can give us your assurance that this will not happen."
The UN recently said that "serious human rights violations have been committed" in Xinjiang, linked to Beijing's so-called counter-terror and counter-extremism policies.
New PM Liz Truss is expected to meet a number of world leaders over the weekend ahead of the state funeral.
It is understood that she is unlikely to meet the Chinese delegation.
Ms Truss has taken a hawkish stance on China, both when she was Foreign Secretary and during the Tory leadership race.
Downing Street said the invitations for the funeral were a matter for Buckingham Palace.
The PM's spokesman said: "First and foremost it is for the Palace on the invite list, inviting heads of state and world leaders to the funeral of Her Majesty. It is for them to set out their guest list.
"As is convention, those we have diplomatic relations with are invited."
