Downing Street has confirmed that King Charles has been advised not to attend the COP27 climate summit in Egypt next month - but Environment Secretary Therese Coffey has said it is "up to him" whether he attends.
Downing Street had previously refused to comment on reports that former prime minister Liz Truss had told the King not to go to the summit next month during a meeting in Buckingham Palace in September.
But, on Friday, a Number 10 spokeswoman acknowledged that the monarch had been urged not to attend the United Nations conference in Sharm El-Sheikh.
The spokeswoman said it was "unanimously agreed" that King Charles, a long-term campaigner against climate change, would not attend.
"As is standard practice, government advice was sought and provided under a previous PM, and it was unanimously agreed that it would not be the right occasion for the King to visit in person," she said.
"I'm not aware that that advice has changed but obviously any confirmation of the King's travel would be for the Palace."
But, earlier on Friday, Environment Secretary Therese Coffey told Sky News that whether the King attends or not was "up to him".
"I'm conscious that King Charles has always taken a very deep interest in the environment and climate change," she said.
"Of course, it would be up to him to decide how he chooses where to put his priorities in his reign as King."
Ms Coffey added that "many members of the Royal Family" attended the summit in Glasgow last year.
She said the "big COPs" tend to happen every five years, adding: "But, in between, it tends to be more of a - I'm not going to say low key - but not quite the same level of heads of state and prime ministers attending."
Downing Street confirmed on Thursday that new Prime Minister Rishi Sunak will also not be attending the climate summit in Egypt.
Scotland's First Minister Nicola Sturgeon will be attending.
Number 10 has insisted the government remains "absolutely committed" to leading international action on the climate issue despite Mr Sunak's absence.
Downing Street suggested the public would expect Mr Sunak to be in the country dealing with the "serious economic challenges" facing the UK, rather than at the summit in Egypt.
Earlier this week, the new PM also demoted COP President Alok Sharma and climate minister Graham Stuart's roles so that they will no longer attend cabinet meetings.
Labour leader Sir Keir Starmer joined environmental campaigners in criticising Mr Sunak's decision to miss the conference.
"Britain showing up to work with world leaders is an opportunity to grasp, not an event to shun," he said.
Former cabinet minister Nadine Dorries agreed that Mr Sunak should be attending the climate summit.
While Rebecca Newsom, head of politics at Greenpeace UK, said the move suggests Mr Sunak does not take climate change "seriously enough".
But, in response, the Number 10 spokeswoman said: "The government remains absolutely committed to leading international and domestic action to tackle climate change and to protect nature.
"We are facing serious economic challenges. The Prime Minister is focused on dealing with those issues, and the public, I think, would also expect him to be in the country... dealing with those and ahead of the autumn statement.
"But we're also very clear that the public should also judge us by our actions and we are forging ahead of many other countries on net zero, for example.
"We will, of course, also be represented at senior ministerial level with the foreign, business and environment secretaries all due to attend alongside the COP president."
King Charles and Prince William both spoke at last year's COP26 event, with the Queen recording an opening address urging world leaders to take action to tackle climate change.