The UK’s windfall tax on oil and gas profits must be changed to raise billions more and to stop companies using loopholes to invest in further fossil fuel extraction, the outgoing president of global climate talks has said. “These are excessive profits, and they have to be treated in the appropriate way when it comes to taxation,” said Alok Sharma, the president of the Cop26 UN climate summit. “We ought to be going further and seeing what more can be done in terms of raising additional finance [from the profits]. So far, at least, the level of money raised is obviously not significant.” The UK is facing a cost of living crisis and the Treasury needs to fill an estimated £50bn hole in the country’s finances. Shell admitted this week it had paid no windfall tax despite having made a record $30bn in profits for the year so far. The oil company said it had taken advantage of a loophole exempting companies that invest their surplus in increasing oil and gas extraction. On Friday, the US fossil fuel firm ExxonMobil reported a quarterly profit of nearly $20bn, $4bn more than forecast. Sharma said: “There really is an incentive for these companies to do more in terms of oil and gas. What we want them to do, if we are to meet our target of 100% clean energy by 2035, is to accelerate the renewables rollout.” He also said the UK’s push for more gas extraction – the government is licensing new drilling in the North Sea, and offering tax breaks for increased production from existing wells – was at odds with the legally binding commitment to reach net zero greenhouse gas emissions by 2050. “The International Energy Agency has been clear that in terms of new fields, they don’t think that’s consistent with a 1.5C pathway, and the onus is on every government – including the UK – to explain how any policies they have on oil and gas, or any other policy, is consistent with their legally binding commitments.” He said companies should be offered incentives to increase their investment in renewables rather than fossil fuels. “That is the way you get faster delivery of renewable energy across the UK,” he told the Guardian. “What we want to see is a big expansion in renewables.” Sharma was praised around the world for his role in directing the Cop26 UN climate talks last November in Glasgow, where he forged a global pact to limit temperature rises to 1.5C above pre-industrial levels. His role as president of the talks ends next week, when the Cop27 summit begins in Egypt. This week he was stripped of his cabinet position by Rishi Sunak, raising concerns among environmentalists about the incoming prime minister’s commitment to tackling the climate emergency. Sharma and Graham Stuart, the climate minister, will keep their current roles but not attend cabinet, leaving the government for the first time in years without a cabinet minister focused on the climate crisis. Downing Street said on Thursday that Sunak would not attend Cop27, in asnub to the Egyptian hosts and to the US president, Joe Biden, who will attend. One developed country diplomat closely involved with the Cop27 talks told the Guardian: “It appears as if the new prime minister wants to wash his hands of the previously strong role the government played on international climate action. Plus, it’s another stab in the back for Sharma.” Sharma, however, defended the prime minister. “Rishi Sunak has actually made a pretty good start on these issues. He has already ruled out fracking … and he said in response to a question at PMQs [prime minister’s questions] that we will deliver on what we said at Cop[26]. The reason for that is that he obviously cares very deeply about passing on to our children an environment in a better state than we found ourselves. That is a really positive statement.” Sunak’s predecessor, Liz Truss, in effect forbade King Charles from attending Cop27, which raised diplomatic protests around the world, as the king has been a major figure at previous Cops, including Glasgow and the 2015 summit that produced the landmark Paris climate agreement. Downing Street confirmed on Friday that the king would not attend, although Egypt’s foreign minister in charge of Cop27, Sameh Shoukry, told the Guardian the invitation was still open. Speaking before Downing Street’s confirmation, Sharma said King Charles was regarded as an international leader on climate. “He’s been focused on this for decades, well before this was mainstream. And of course he’s also head of [state] of a number of other nations, some of whom are on the frontline of climate change. I would very much like him to be there but ultimately that is a matter between him and the government.” With the war in Ukraine, and a standoff between the US and China over Taiwan, the prospects for Cop27 have dimmed. Sharma left Cop26 warning that the 1.5C limit – beyond which the impacts of the climate crisis will swiftly become catastrophic and irreversible – was “on life support”. In the past week the UN has released two reports showing that governments have failed to reduce greenhouse gas emissions fast enough to meet the 1.5C goal, with current short-term pledges on emissions likely to raise temperatures by 2.5C. Only 24 countries have come forward with fresh emissions-cutting plans since Cop26, despite all at Glasgow having promised to do so. Sharma said it was still possible to make progress at Cop27 on reducing emissions. “What we have seen [since Cop26] is the geopolitics change quite significantly … with Putin’s illegal war in Ukraine. That has resulted in world leaders having to deal with immediate issues in terms of an energy crisis, food security issues, rising inflation, rising debt levels. That’s completely understandable. However, what we’ve also seen is that the chronic threat of climate change has not gone away; it’s got worse.” Sharma has spent much of his time as Cop26 president – his term was prolonged after the Covid pandemic delayed Cop26 by a year – speaking to and visiting developing countries on the frontline of the crisis. “I was at the UN general assembly a few weeks ago, and I had an opportunity to speak with the Pakistani minister for climate change. It was really incredibly moving to hear her speak about the terrible peril that so many millions are now facing in Pakistan as a result of one-third of the country being under water – the same size of land under water as the UK itself,” he said. “You’ve got 5 million people facing a food crisis, and more recently you’ve seen flooding in Nigeria, the worst floods in a decade, with a million people displaced. So what countries are going to need to do is, while they deal with the immediate issues [of energy and food prices], they also then continue to deal with the issue of global warming.” Soaring gas prices have sent governments – including the UK – back to fossil fuels, but Sharma said this was likely to be temporary as renewable energy was cheaper. “The war has meant countries are accelerating their clean energy transitions and going faster than they would otherwise have done. To meet immediate energy needs, you are seeing some countries doing more fossil, more coal, but you’re also seeing them absolutely doubling down on more renewables.” Sharma, who supported Boris Johnson’s truncated attempt to return as UK prime minister, faces an uncertain political future when his term as Cop president ends. But he vowed to continue to speak out: “I am no longer a [cabinet] minister but I have a voice. I will use that voice. Ultimately, we will be judged as a government on whether we keep the promises that we have made and whether we deliver on our commitments.”