The government is drawing up plans to drop the UK’s flagship £11.6bn climate and nature funding pledge, the Guardian can reveal, with the prime minster accused of betraying populations most vulnerable to global heating. The disclosure provoked fury from former ministers and representatives of vulnerable countries, who accused Rishi Sunak of making false promises. A leaked briefing note to ministers, given to the Foreign Office and seen by the Guardian, lays out reasons for dropping the UK’s contribution to meeting the global $100bn (£78.6bn) a year commitment to developing countries. It says: “Our commitment to double our international climate finance to £11.6bn was made in 2019, when we were still at 0.7 [% of GDP spent on international aid] and pre-Covid.” It adds that to meet it by the deadline would be a “huge challenge” because of new pressures, including help for Ukraine being included in the aid budget. To meet the £11.6bn target by 2026, government officials have calculated that it would have to spend 83% of the Foreign Office’s official development assistance budget on the international climate fund. Civil servants said in the leaked document that this “would squeeze out room for other commitments such as humanitarian and women and girls”. It also claimed that factors such as Ukraine and debt relief could make it even more difficult to meet the target. This is because the government has cut international aid spending to 0.5% of gross national income since the announcement was made, squeezing budgets across the board, and because ministers did not spend most of the money allocated to the climate fund over the past few years, leaving the majority to be spent by 2026. The UK spent £5.8bn over the previous five years up to 2021. This was doubled, to spend £11.6bn between April 2021 and March 2026, £3bn of which was earmarked for protecting and restoring nature for meeting commitments made in Cop15 last December. The projects funded include building renewable energy, helping create low-pollution transport and protecting forests in sensitive areas around the globe. Former Foreign Office minister Zac Goldsmith, who resigned last week citing what he termed Sunak’s “apathy” towards the environment, said this would “shred” the UK’s international reputation. He told the Guardian: “The low levels of expenditure so far combined with the decision to define our spending on Afghan and Ukrainian refugees here in the UK as aid (something other countries have not done) means it is going to be virtually impossible to honour the promise. The hockey stick of spending will be so steep that whoever is in government after the next election would have to savagely slash humanitarian, education, health and other funding in order to hit the £11.6bn target. So even while it is technically possible to claim we will honour the pledge, the next government will simply not be able to. “Small island states in particular, whose votes in the UN are no less valuable than ours and which are routinely needed by us, will be left feeling utterly betrayed. Given around 25 Commonwealth countries are small island states as well as our interests in the Pacific and Caribbean, the geopolitical repercussions will be far reaching and our reputation as a reliable partner will simply be shredded.” Last week the government’s statutory climate advisers published a report finding that the government was missing the majority of its climate targets and had lost its position as a world leader on climate. Countries due to receive the funding have expressed dismay at the prospect of a funding cut. Lee White, Gabon’s environment minister, said: “The climate crisis is such that every country has to contribute to the solution. Gabon is 88% covered by tropical rainforest. We have maintained deforestation below 0.1% over 5 decades and net absorb over 100m tonnes of CO2 annually. Few countries are doing more for the planet. Developed nations, particularly the UK, which was at the origin of the Industrial Revolution, have to do the heavy lifting – but all too often they make false promises and fail to provide true leadership or even honour their modest financial commitments.” The decision is likely to diminish the UK’s standing on the world stage, as international groups accuse it of squandering its reputation. Clare Shakya, the strategic director of the International Institute for Environment and Development, said: “A decision by this government to drop the pledge of £11.6bn in climate finance is somewhat unsurprising given cuts they had already made to programmes that would have used that funding. But it’s no less disappointing. Not only could that funding have helped some of the most vulnerable people already facing the droughts, flooding and wildfires brought on by climate change, its provision was also a demonstration of the UK’s leadership in the face of the climate crisis. “The UK government seems content to squander what standing it had on the world stage to bring countries together to face this global emergency.” The briefing note suggests a departure from the UK’s previous plans to be at the “forefront of addressing the challenges associated with climate change and biodiversity loss”. When the funding was announced, the government departments involved called climate finance “the top priority for government over the next decade” and described the fund as a “vital tool in the government’s commitment to tackle climate change internationally”. The Foreign Office declined to comment on the leak, but pointed to Rishi Sunak’s comments made at Cop27 regarding climate finance. A spokesperson said: “We spent over £1.4 billion on international climate finance over the course of the 2021/22 financial year, supporting developing countries to reduce poverty and respond to the causes and impacts of climate change. We will publish the latest annual figures in due course.” It later added: “Claims that the international climate finance pledge is being dropped are false. As the prime minister set out at Cop27, the government remains committed to spending £11.6bn on international climate finance and we are delivering on that pledge.”