King Charles and Sir Keir Starmer are set to face demands for the UK to pay an astonishing £200 billion in compensation for its role in the slave trade when they attend a Commonwealth summit later this month.

A group of 15 Caribbean governments has unanimously agreed to put slavery reparations on the table at the Commonwealth Heads of Government meeting in Samoa on October 21.

It comes after the the Prime Minister of Barbados told the United Nations that reparations for slavery and colonialism should be part of a new ‘global reset’.

Mia Mottley, who is leading the demands from the West Indies nations, met the King in London earlier this month for talks in advance of the 56-nation Commonwealth gathering.

Ms Mottley has praised Charles for declaring two years ago that slavery is ‘a conversation whose time has come’, although Buckingham Palace declined to reveal the contents of their latest ‘private discussions’.

The calls come in the wake of the Prime Minister’s controversial decision to hand over the Chagos Islands to Mauritius earlier this month, a move which has led to fears for the future of British control of other strategic territories including the Falkland Islands and Gibraltar.

Foreign Secretary David Lammy – who is descended from enslaved people – has described how his ancestors heard ‘the twisted lies of imperialism as they were stolen from their homes in shackles and turned into slaves’.

He also controversially supported protesters who toppled the statue of slave trader Edward Colston in Bristol and dumped it into the harbour four years ago. Dozens of other memorials to traders and colonialists were removed in the wake of the Black Lives Matter protests.

Estimates of the likely reparations bill for British involvement in slavery in 14 countries range from £206 billion to a staggering £19 trillion. The higher figure was cited last year by UN judge Patrick Robinson, who called it an ‘underestimation’ of the damage caused by the slave trade.

Mr Robinson said he was amazed that countries involved in slavery think they can ‘bury their heads in the sand’ on the issue, adding: ‘Once a state has committed a wrongful act, it’s obliged to pay reparations’.

The demands come amid increasing republican sentiment in the Caribbean. Ms Mottley removed the Queen as Barbados’s Head of State in 2021 and Jamaica has pledged to ditch the monarchy by next year.

Ms Mottley has described her country as ‘the home of modern racism’ thanks to British rule from 1625 and says the UK’s debt to her country is £3.7 trillion.

Even a tiny fraction of that would prove ruinous for Chancellor Rachel Reeves, who is planning tax rises to plug a £22 billion ‘black hole’ in public finances.

Last night, No 10 said that as an agenda for the Commonwealth Heads of Government Meeting (CHOGM) had not yet been published, the issue was a matter of ‘speculation’.

But this summer, Dr Keith Rowley, the Prime Minister of Trinidad and Tobago, declared during slavery emancipation celebrations: ‘When we meet in Samoa, the Caribbean leaders [will] very forcefully speak to the Commonwealth as one voice. And there is one particular country with a new King and a Labour government with an outstanding mandate.’

The Church of England last year announced it was setting up a £100 million fund for reparation payments to recognise that it once profited from the slave trade.

Speaking when he was still Shadow Foreign Scretary, Mr Lammy said he would ‘take the responsibility of being the first Foreign Secretary descended from the slave trade incredibly seriously’.

He said his Guyanese parents would not have believed ‘their skinny son in NHS prescription glasses who got stopped and searched on the streets of Tottenham’ could reach the Foreign Office, adding: ‘They would have been surprised because our ancestors knew what it was like to have their freedom taken away.’

He has also tweeted: ‘In 1833 Parliament passed the Slavery Abolition Act. £17billion of compensation to slave owners for the loss of their property – my ancestors. The slaves received no reparations. Some people simply do not know their history or do not want to know hard truths.’

However, research contained in a new report by the leading think-tank Policy Exchange has found that a majority of Commonwealth citizens believe that Britain ‘does more good than harm’ in the world – the reverse of the view among British people.

A spokesperson for the Commonwealth Secretariat said last night: ‘Commonwealth heads have always discussed challenges and aspirations constructively’, adding that it would use its collective power to ‘discuss matters of importance and significance to its member states’.

The Foreign Office did not respond to a request for comment.