The Egyptian government, host of the next UN climate summit, has warned the UK against “backtracking from the global climate agenda”, in a significant intervention prompted by fears over Liz Truss’s commitment to net zero. The warning before the Cop27 conference, which will take place in just over a month in Sharm el-Sheikh, to the host of Cop26, which took place in Glasgow last November, is highly unusual in diplomatic terms. The hosts of successive Cops are responsible for a smooth handover of the talks. The intervention, sparked by reports that King Charles III has been effectively forbidden by the UK prime minister from attending Cop27, reflects fears among participants in the talks over a change of direction from Britain. The previous prime minister, Boris Johnson, was regarded as a strong champion of the UK’s goal, shared with many other rich nations, of net zero greenhouse gas emissions by 2050. But Truss, though she has said she supports the net zero target, has dismayed climate campaigners by offering more than 100 new licences for oil and gas in the North Sea, lifting the ban on fracking, and cancelling green regulations. She may also fail to attend Cop27, a significant snub to the Egyptian hosts who are holding a leaders’ summit for heads of state and government as part of the conference. The Egyptian government praised King Charles – who spoke at the start of the Paris climate summit in 2015, and was an important presence at Cop26 – as a champion of the environment, and pointedly re-extended an invitation to him. A Cop27 spokesperson said: “The Cop president designate is disappointed by these reports [of Charles’s non-attendance at Cop27]. The Egyptian presidency of the climate conference acknowledges the longstanding and strong commitment of His Majesty to the climate cause, and believes that his presence would have been of great added value to the visibility of climate action at this critical moment. We hope that this doesn’t indicate that the UK is backtracking from the global climate agenda after presiding over Cop26.” He added: “His Majesty King Charles was invited as a very special guest to Cop27. The invitation was extended to His Royal Highness as Prince of Wales, and renewed to His Majesty as King, and he will be most welcomed in Sharm el-Sheikh if he honours us with his presence.” The spokesperson also noted Truss was still invited in her capacity as head of the UK government. “All leaders of the state parties to the UNFCCC [United Nations framework convention on climate change] and the Paris agreement are invited to this UN summit. The host country will announce the number of heads of states and governments taking part as we get closer to the Sharm el-Sheikh climate implementation summit,” he said. “So far Egypt has received a very encouraging number of confirmations from heads of states and governments, from every region.” The Guardian understands some Commonwealth countries are also privately concerned that Truss has prevented the King from attending Cop27, as he acts as their head of state. Many Commonwealth countries are among the world’s most vulnerable to the climate crisis. A Downing Street spokesperson said Truss’s travel plans would not be settled until nearer the date of Cop27 and refused to comment on private conversations between the prime minister and the King. The prospect of British leaders, including King Charles, descending on Sharm el-Sheikh also raised questions about the optics of such a visit while the British activist Alaa Abd El Fattah remains on hunger strike inside an Egyptian prison. Abd El-Fattah, a figurehead of Egypt’s 2011 uprising, has been on hunger strike for 185 days and recently told his family he believes he will die in prison before Cop27. He began his hunger strike in protest at his treatment in detention, including efforts by the Egyptian authorities to stonewall a consular visit by British officials to assess his health. Truss told parliament when she was foreign secretary last June that “we’re working very hard to secure his release”, but since then has made no further statements on the matter. The case threatens to undermine Egypt’s efforts to use Cop27 to present a favourable image of the country amid claims it has limited access for civil society and may restrict protests. At a pre-Cop27 meeting in the Democratic Republic of the Congo on Monday, the Egyptian foreign minister, Sameh Shoukry, the president of Cop27, called on developed countries to assist poorer countries in tackling the climate crisis. Rich states have a longstanding pledge to provide $100bn (£89bn) a year to developing countries, to help them cut their greenhouse gas emissions and adapt to the impact of extreme weather, which has not yet been fulfilled. Shoukry said: “We have not yet delivered on the $100bn pledge, which in itself is more a symbol of trust and reassurance than a remedy to actual climate needs.” He added that much of the finance being provided was in the form of loans, which can drive poor countries deeper into debt. He said: “Instruments of finance are still mostly non-concessional loans rather than concessional loans and grants which account for only 6% of climate finance. We must find a way to address this challenge. Without appropriate and fair finance serving as a catalyst, we will all continue to struggle in delivering impactful climate action.” The UN secretary general, António Guterres, also warned more help was needed for poor countries suffering catastrophic effects from extreme weather. Known as loss and damage, a phrase that refers to impacts too serious for countries to be able to adapt to, the issue is likely to be one of the biggest areas of disagreement at Cop27. Guterres said: “Cop27 must be the place for action on loss and damage. This is the number one litmus test of how seriously both developed and developing governments take the growing climate toll on the most vulnerable countries.” Guterres also warned that the World Bank and other development banks “must raise their game”. The World Bank has come under fire for perceived failures to address climate finance, and for the conduct of the bank president, David Malpass, who was appointed by the former US president Donald Trump. “International financial institutions must overhaul their business model and approach to risk,” Guterrres added. “Beyond pursuing their own drop-in-the-bucket initiatives, they must intensify their efforts to leverage the necessary massive increases of private finance as first investors and risk takers.” A spokesperson for the UK government said: “We have a proud record when it comes to Cop, [and] we are forging ahead with our plans for net zero. Forty per cent of our power now comes from clean energy sources and we will continue to deliver on those promises.”