They said the decision was made on the government’s advice and was “entirely in the spirit of being ever-mindful as King that he acts on government advice”.

The Queen delivered a pre-recorded message to COP26 hosted in Glasgow last year in which she praised the advocacy of her family, including her late husband Philip, the Duke of Edinburgh, her son and grandson in promoting the urgency for climate action.

“It is a source of great pride to me that the leading role my husband played in encouraging people to protect our fragile planet, lives on through the work of our eldest son Charles and his eldest son William. I could not be more proud of them,” she said.

The King, 73, has been a prominent voice on environmental issues for more than 50 years, also delivered a speech at the opening ceremony in Glasgow, calling on world leaders to adopt a “warlike footing” to deal with the threat of climate change.

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But he said in a historic address to the nation following the death of his mother last month that his role would change now that he had become the sovereign.

The palace source told the newspaper: “The Queen gave an entirely non-political address at COP last year ... it sounds like he is not being given the choice. That is an error of judgment on the part of the government.

“The King could absolutely go and deliver the government’s message and give it credibility, given all the kudos he has in that space.

“It’s disappointing if people don’t believe he’d be able to do that, of course he could. He delivered the Queen’s speech at the state opening of parliament, rattling off lots of policies that went against his personal beliefs.

His son, William, the Prince of Wales is likely to pick up where his father left off. He will continue to focus on his Earthshot prize for environmental innovations and will attend its award ceremony in Boston in December, along with his wife Catherine, the Princess of Wales.

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In a speech to the Earthshot Prize Innovation Summit last week, William said protecting the environment was a cause close to his late grandmother’s heart, and he hoped to continue that legacy.

He said the prize’s mission, “to repair, restore and rejuvenate our planet within this current decade” was not simple, particularly in light of the global geopolitical uncertainties.

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