Liz Truss reportedly told King Charles to abandon his plans to attend the Cop27 climate summit next month.
Charles wanted to give a speech at the conference in Egypt but has had to put to the plans on ice after Ms Truss intervened, The Sunday Times has reported.
Ms Truss apparently put a stop to the speech during a personal audience with the King last month.
Buckingham Palace confirmed on Saturday night that Charles would not attend the conference.
Charles is a prominent climate campaigner and had been invited to attend the Cop27 summit.
“He had to think very carefully about what steps to take for his first overseas tour, and he is not going to be attending Cop,” one royal source told The Sunday Times.
The decision was made “entirely in the spirit of being ever-mindful as King that he acts on government advice”.
One source who knows Charles said he was “all lined up to go”, the paper reported.
“It sounds like he is not being given the choice. That is an error of judgement on the part of the government,” they said.
It would be normal practice for Charles to seek Ms Truss’s guidance on whether to go to Cop27, a royal source told The Independent, highlighting that any suggestion that Charles’ attendance to the summit is a point of disagreement with Ms Truss is untrue.
A Number 10 source told Sky News that “the idea the PM gives orders to the King is ridiculous.”
Ms Truss is reportedly unlikely to attend the climate conference herself and so this could have influenced the government’s position on Charles’s visit.
Charles is a prominent climate campaigner and his interests range from tropical forests, sustainable farming practices to water security. A regular speaker on climate issues, he gave a speech at the opening ceremony of Cop26 in Glasgow.
In his first speech as King, Charles indicated that he would pass on his climate campaigning to his son Prince William.
“With Catherine beside him, our new Prince and Princess of Wales will, I know, continue to inspire and lead our national conversations, helping to bring the material to the centre ground where vital help can be given,” he said.
Cop27 is to be held from 6 to 18 November.
Number 10 has been contacted for comment.