King Charles will have to temper his public support for net zero after Kemi Badenoch broke the political consensus over the UK’s greenhouse gas emissions.

Senior royal sources have conceded that the 76-year-old monarch, who has spent more than half a century highlighting environmental challenges, will have to choose his words more carefully now that the Conservatives under Badenoch have said it will be impossible for the UK to hit net zero by 2050.

“The only way that we can regain it [trust] is to tell the unvarnished truth – net zero by 2050 is impossible,” the Conservative leader said last month.

Charles III has spoken publicly about how vital it is to hit net zero by the 2050 target date, set by Theresa May’s government in 2019 and agreed upon by subsequent administrations. Successive prime ministers have used the king’s long track record on campaigning for climate action to help promote Britain’s leadership on combatting the challenges.

In December 2023, for example, the king told the Cop28 UN climate change conference in Dubai that more urgent action was needed to bring the world towards a zero-carbon future. “After all, ladies and gentlemen, in 2050 our grandchildren won’t be asking what we said, they will be living with the consequences of what we did or didn’t do,” he said.

At that point, the main UK political parties were agreed on the issue. Now the monarch runs the risk of becoming embroiled in a party political dispute. In addition to the change in the Conservative view, Reform wants to scrap net zero completely.

Craig Prescott, a constitutional expert at Royal Holloway, University of London, suggested the king must be less specific about his own views on the target. “I think if you take the view that the monarchy has to be ‘two or three steps away’ from party politics then, as party politics changes, the monarchy should change,” he said.

Charles, who flies to Italy tomorrow with Queen Camilla for a state visit that lasts until Thursday, will still put tackling the climate crisis and other environmental challenges at the heart of his monarchy.

The work to create a more sustainable future will be a feature of the trip. In Rome, the king will join a meeting chaired by the foreign secretary, David Lammy, and attended by business leaders to hear how Britain and Italy are working together on the transition to clean energy. In Ravenna he will meet farmers whose land and crops have been severely affected by devastating floods in the region in the past few years.

He and Camilla, who celebrate their 20th wedding anniversary at a state banquet in Rome on Wednesday evening, will visit the Colosseum and celebrate close defence ties between the two countries, in spite of the political differences between Keir Starmer’s Labour party and Italy’s rightwing leader, Giorgia Meloni.

The need to avoid involving the king in party political controversy has been highlighted after documents released on Friday revealed that the monarch secretly met Prince Andrew to discuss his future and was twice briefed about plans for him to be involved in a £2.4bn investment fund run by an alleged Chinese spy, Yang Tengbo. Buckingham Palace insisted Yang, since banned from Britain despite protesting his innocence, was not specifically mentioned.

Prince William is likely to attend the Cop30 UN climate conference in Belém, Brazil, in November and may also be more guarded than before about his views on achieving net zero, although royals may still be expected to reflect on government policy on the international stage.

Any silencing of the monarch and his heir threatens to weaken Britain’s voice abroad, according to some environmental groups. Shaun Spiers, executive director of the environmental thinktank Green Alliance, said Charles might be unable to speak out specifically on the 2050 target but could talk generally about the need for climate action. “The king is a well-respected leader and it would be a shame if he didn’t speak on it, particularly internationally,” he said.

Reshima Sharma, deputy head of politics at Greenpeace UK, pointed to popular support for green policies. “King Charles has long been an important advocate for action to clean up our environment and tackle climate change. While the monarchy must remain politically neutral, thankfully climate action continues to receive the kind of popular support that politicians can only dream of. This is reflected across voters of all stripes,” she said.

Buckingham Palace declined to comment.