KING Charles III will confront "shameful aspects" of United Kingdom history with "unflinching honesty" when he addresses Commonwealth leaders next week, said Buckingham Palace on Saturday.

The comments follow renewed scrutiny of Britain's role in historical transatlantic slavery and come after Prime Minister Andy Burnham revealed he was open to the UK formally apologising for its role in the trade while ruling out paying the financial reparations demanded by some Caribbean countries.

The issues have resurfaced as Charles tours the Caribbean before delivering a speech tomorrow at the Commonwealth heads of government meeting there, which Burnham is also set to attend.

"The king will not shy away from confronting the most shameful aspects of the past during this visit," said a palace spokesperson.