Boris Johnson has confirmed he will attend the Cop27 conference in Egypt, piling further pressure on Rishi Sunak to backtrack on his decision to snub the climate summit.

The former prime minister said he was “happy to go” to Sharm El Sheikh for the United Nations meeting opening on Sunday.

However, Mr Sunak is leaving his own decision to the last minute, having initially ruled out attending before signalling he could U-turn in the face of widespread criticism.

The Prime Minister’s own climate adviser Alok Sharma had said he was “disappointed” that Mr Sunak was not planning to attend.

But the decision of his arch-rival and former Downing Street neighbour to attend will make it even harder for Mr Sunak to resist going.

Mr Johnson told Sky News “yes, as it happens” he will be attending, adding: “I was invited by the Egyptians so I’m very happy to go.”

Asked if his successor in No 10 should go too, he said Mr Sunak has a “massive amount to do” with the Government’s domestic agenda, adding: “I happen to have a particular interest.”

Mr Johnson argued it has become “unfashionable” to talk about the Cop26, which he hosted in Glasgow last year.

“I want to talk a little bit about how I see things and how we see things in the UK,” Mr Johnson added.

Initially Downing Street said Mr Johnson would not be attending because he must focus on the “depressing domestic challenges”, as he works on the autumn budget.

But on Monday he changed tack, with No 10 saying that the decision was now “under review” as “substantial progress” was being made on his economic plans.

The Prime Minister’s official spokesman could not confirm on Tuesday afternoon whether Mr Sunak would be attending, saying talks are ongoing between him and Chancellor Jeremy Hunt.