A row over prime minister Rishi Sunak’s refusal to attend the Cop27 climate summit took an extraordinary twist on Saturday night as the Observer was informed that his predecessor but one – Boris Johnson – is planning to attend the event. Several sources said they had been told that Johnson is intending to go to the crucial meeting of world leaders in Egypt to show his solidarity with the battle against the climate crisis. Johnson’s attendance would be potentially explosive just days after Sunak took over as prime minister and decided he did not have time to attend. Johnson’s involvement would be seen as both an implicit criticism of Sunak for not going and an attempt to maintain and bolster his profile just a week after he abandoned his own attempts at a dramatic comeback to No 10. Several sources close to Johnson did not deny that he was set to go. On Saturday night there were signs of a row at the highest levels of government over Johnson’s intentions, and indications that efforts may be under way to get the former prime minister to change his mind. Asked whether Johnson was attending Cop27, the Cabinet Office, which is in charge of Cop planning and preparations, said it could not answer directly. A spokesman said: “The government is absolutely committed to supporting Cop27 and leading international action to tackle climate change and protect nature. “The UK will be fully represented by senior ministers, including the foreign, business and environment secretaries, as well as Cop president Alok Sharma. They will be working to ensure that countries continue to make progress on the groundbreaking commitments made at Cop26 in Glasgow.” It is understood senior officials in government have been aware for some time that Johnson intends to attend the event in Sharm el-Sheikh, which is taking place from 6-17 November. It remained unclear on Saturday night whether Johnson was planning to go as part of the official UK government delegation, which includes several MPs; as a guest of the incoming Egyptian Cop presidency; or as a guest of a non-governmental organisation or other national delegation. The new prime minister’s decision not to attend has already provoked huge criticism from the environmental lobby and caused dismay in other governments. Even MPs in his own party have been critical. Nadine Dorries, the former culture secretary who led calls for Johnson to return as leader as Liz Truss’s government fell apart, said that “the prime minister is wrong not to go”. “Global warming is the biggest crisis facing our planet and net zero creates many 100s of jobs which is good for the economy,” she tweeted. She said that the Cop26 conference in Glasgow, which took place under Johnson’s leadership, was “the most successful ever”. Suggestions that Sunak urged King Charles not to attend the summit when he was keen to do so were denied by Buckingham Palace last night. A spokesman for the palace said the decision that the king would not attend was agreed between all parties and taken entirely by mutual consent. The palace said the king would demonstrate his own commitment to the Cop process by hosting an event at Buckingham Palace this week for business leaders, decision makers and NGOs that would be attended by the prime minister and Sharma. It is by no means unusual for former leaders to attend Cop summits. Former US president Barack Obama notably attended the Cop26 summit in Glasgow last November. Ed Miliband, the shadow secretary of state for the environment and net zero, said: “Rishi Sunak is absent when it comes to the climate crisis. If even the former prime minister is attending Cop27, it is just further evidence of his colossal failure of leadership. “The prime minister’s decision to pull out of Cop27 shows he doesn’t care about the greatest long-term threat our country faces. “The government is way off track from its climate targets, and has a deeply unambitious net zero agenda, with plans to cut the cheapest, cleanest forms of power like onshore wind. “A Labour government would lead at home and abroad, putting climate at the heart of our agenda for a fairer, greener future with lower bills and energy independence for the UK through our plans for clean power by 2030 and GB Energy to make us a clean energy superpower.” Paul Bledsoe, a former Clinton White House climate adviser who is now with the Progressive Policy Institute in Washington, said: “Boris Johnson’s erstwhile climate advocacy, which emerged only at Glasgow, is nonetheless a welcome example that US conservatives and others rightwing parties would do well to imitate. “Climate change impacts are already undermining public safety, economic production, and border and national security in nations around the world. If conservative governments like the UK Tories can’t rally around protecting those values, what good are they? The climate crisis must coalesce cross-party, national unity political action by all major nations. Unlike American Republicans, at least Johnson seems to get that.” At the Glasgow Cop26 summit, countries pledged to limit global temperature rises to 1.5C above pre-industrial levels, which would give the world a chance of avoiding the worst ravages of climate breakdown. But since then, Russia’s invasion of Ukraine and the energy and cost of living crises around the world have deeply divided governments, and left many of their climate pledges in tatters. Last week, two UN reports showed the extent of that failure: current plans on greenhouse gas emission reductions this decade would lead to heating of 2.5C and scientists warned the chance of staying within 1.5C was now slim. Patricia Espinosa, whose second three-year term as executive secretary of the UN framework convention on climate change (UNFCCC )ended this summer, called on leaders and citizens to keep faith in the talks. “This is an agenda where we can’t afford to give up. This is the future of humanity,” she said. “It sometimes feels like we will never get there. But the only thing we can do is not to give up.” The UN talks have carried on for three decades, since the UNFCCC – parent treaty to the 2015 Paris agreement – was signed in 1992. But greenhouse gas emissions have continued to rise in almost every year since. Espinosa said the climate crisis was frequently overshadowed by other crises, including wars and economic woes. “Despite all that, the fact remains that this is the biggest threat to humanity. It’s very important that we act according to the emergency that we are facing,” she told the Observer in an interview. “We do not have the luxury of addressing these other crises now and dealing with the climate later.” Governments must find common ground at Cop27 despite their tensions and conflict, Espinosa said. “We need to send a message that through the UNFCCC process we are making progress. We need to give people a sense of hope.” She pointed to discussions on finance for poor countries, to help them cope with the impacts of extreme weather, as a key area where developed countries could make a difference. “The promise of a doubling of finance for adaptation was a very important element of Cop26, and it’s not clear whether or how we will see progress on that at Cop27,” she warned.