Under current plans, climate finance for developing countries will fall from £11.6bn allocated over the past five years to £9bn over the next five-year period. When inflation is taken into account, this would amount to a reduction of roughly 40% in real spending power compared with the level agreed in 2021.

The proposed cuts, driven by decisions at the Treasury, come even as senior UK security officials have warned that large-scale ecosystem breakdowns — such as the loss of the Amazon rainforest or the Congo Basin — could pose serious risks to Britain's national security. These include rising global food prices, economic instability and an increased likelihood of conflict.

The move also follows international commitments made by wealthy nations just last year to triple global climate finance for poorer countries to $300bn (£220bn) annually by 2035. While no binding national quotas were set, a reduction from the UK would make meeting the collective target more difficult.

Mohamed Adow, director of the climate thinktank Power Shift Africa, said the implications would be felt immediately on the ground. "For countries on the frontline of climate impacts, UK climate finance is not symbolic," he said. "It determines whether communities can adapt or are pushed into catastrophe. Cutting it now will cost lives and destroy livelihoods."

The decision comes as the US retreats from global climate commitments, with Donald Trump withdrawing the country from the Paris agreement and scrapping climate finance targets. Adow warned that a similar move by the UK could encourage other nations to step back from their responsibilities, weakening international efforts to address climate change.

Within the Foreign, Commonwealth and Development Office, ministers are still negotiating the details of the next phase of international climate funding, known as ICF4 — the fourth funding cycle since 2010. Climate finance is drawn from the UK's overseas aid budget, which was reduced last year to 0.3% of gross national income. Until 2021, the UK had maintained aid spending at 0.7%, before it was lowered to 0.5% and later cut further.

The £9bn pledge would likely translate into around £2bn per year over the next three years, followed by approximately £1.5bn annually in the years 2029–30 and 2030–31. Those later figures fall beyond the current parliamentary term. While the Treasury is reportedly reluctant to lock in funding beyond its three-year spending framework, other government departments and several parliamentary committees have argued that long-term climate finance requires stable, multi-year commitments.