Rishi Sunak has reversed his decision to skip the Cop27 climate summit in Egypt next week, bowing to pressure from activists, his own environment adviser and Boris Johnson.

The Prime Minister accepted there is “no long-term prosperity without action on climate change” as he confirmed he will attend this year’s UN talks in Sharm El Sheikh that start on Sunday.

Mr Sunak had been declining to go, arguing that he needed to focus on the “depressing domestic challenges” as he worked on the autumn Budget with Chancellor Jeremy Hunt.

But Labour accused the Prime Minister of having been “dragged kicking and screaming into doing the right thing” days ahead of the summit.

Cop26 president Alok Sharma, who will be handing over the UK’s presidency to Egypt at the summit, said he is “delighted” about the U-turn, having previously expressed his disappointment.

Mr Sunak announced his attendance the morning after Mr Johnson, one of his predecessors in No 10 and rival in the Conservative Party, confirmed he will be joining the talks in Egypt.

“There is no long-term prosperity without action on climate change,” Mr Sunak tweeted.

“There is no energy security without investing in renewables.

“That is why I will attend @COP27P next week: to deliver on Glasgow’s legacy of building a secure and sustainable future.”

Mr Johnson chose not to publicly criticise Mr Sunak’s initial refusal to attend, but said in an interview broadcast on Tuesday evening that he will be attending to discuss “how we see things in the UK” given he has a “particular interest”.

“I was invited by the Egyptians so I’m very happy to go,” he told Sky News.

Mr Sharma, who presided over Cop26 in Glasgow last year, welcomed Mr Sunak’s reversal, saying he “completely” agrees with his comments that climate action is required to secure long-term prosperity.

Deputy Labour leader Angela Rayner said the U-turn was “embarrassing”, arguing that Mr Sunak had to be “dragged kicking and screaming into doing the right thing”.

It was only on Friday that Mr Sunak was arguing to broadcasters that he was “focusing on the depressing domestic challenges we have with the economy” as he sought to justify not attending.

“I think that’s what people watching would reasonably expect me to be doing as well,” he said.

Shadow climate secretary Ed Miliband said Mr Sunak had agreed to go “to avoid embarrassment not to provide leadership” and seized on his change in language, saying: “The guy is a phoney.”

“The Prime Minister has been shamed into going to Cop27 by the torrent of disbelief that he would fail to turn up,” Mr Miliband added.

“Yet again we see a Prime Minister who only makes decisions for reasons of political management not the national interest.”

The key day for world leaders is Monday, when high-level talks are scheduled, and US President Joe Biden is expected to attend.

Green MP Caroline Lucas tweeted: “Glad to see Sunak’s screeching U-turn on #COP27, but what an embarrassing mis-step on the world stage. Let this be a lesson to him – climate leadership matters.

“Now he urgently needs to increase UK ambition on emission reduction targets & pay what we owe to global climate funds.”

Friends of the Earth international climate campaigner Rachel Kennerley welcomed Mr Sunak having “seen sense and decided to attend”.

“But simply showing up won’t be enough,” she said. “The UK Government has a lot of work to do to rebuild its climate reputation after a year of rowing back on commitments made in Glasgow.”

Despite No 10’s U-turn, the King is still not planning to attend Cop27.

A Buckingham Palace spokesman said there is “unanimous agreement” with the Government that it is not right for Charles, a long-standing environmental campaigner, to go.