Buckingham Palace and Downing Street have said that there has been "unanimous agreement" that Charles would not go to COP27, with the king focussed instead on hosting a climate reception at the palace on Friday.

But Sunak's spokeswoman suggested that if Sunak, who only became prime minister last week, had been in office longer, Charles might have gone to COP27 after all.

"We do recognise that had the prime minister been in post earlier, the situation might have been different, but it is not logistically feasible at this late stage," the spokeswoman told reporters.

"So... there remains unanimous agreement between the palace and the government that the king will not attend."

Downing Street only confirmed Sunak's own attendance at the summit on Wednesday, reversing an earlier position that he would not attend due to pressing domestic issues.

Often outspoken on climate change, Charles had agreed with the previous Prime Minister Liz Truss that he would not attend the climate summit. The Sunday Times at the time reported Truss had asked Charles not to go, though discussions between the two had been cordial.

Charles addressed COP26 in Glasgow when Britain hosted the climate summit a year ago, but has indicated he will step back from some of his campaigning since he became king following the death of his mother, Queen Elizabeth II, in September.