Disaster relief and Christian development agency Tearfund is urging Prime Minister Rishi Sunak to maintain a promise to meet an £11.6 billion climate and nature pledge.

According to a leaked internal memo sent to ministers, the commitment is set be missed, as funding of that scale would be a "huge challenge" and require backing for other aid projects to be slashed.

“Failing to keep this promise would be a miserly betrayal that will cost lives and livelihoods”, commented Tearfund’s head of advocacy, Paul Cook.

“It would be a backwards step for international cooperation at a time when working together is more crucial than ever”, he said.

However, the government rejects suggestions that the commitment could be dropped, saying these are “false” and that it remains committed to delivering on the pledge.

Details from the memo, obtained by the Guardian, indicate that the funding up to March 2026 was pledged when the government was keeping to legally-enshrined targets of spending 0.7% of national income on overseas aid.

But this commitment was cut to 0.5% following Covid.

According to the memo, if the £11.6bn was kept to, the spending "would squeeze out room for other commitments such as humanitarian and women and girls". It is this which is causing concern to Tearfund.

“The outrageous claim that climate finance money should be spent elsewhere on humanitarian priorities is misleading”, continued Paul Cook.

“Climate finance should be new and additional to international aid specifically to prevent this from happening in a context where extreme weather related disasters are on the rise”, he said.

“Cutting funding for reducing emissions and adapting to live with climate impacts is dangerously short-sighted and undermines global efforts to save lives”, he added.

The dispute comes as the world recorded its highest ever average daily temperature earlier this week. The US National Centers for Environmental Prediction says the planet reached 17-point-zero-one degrees.

Heatwaves in the southern US, China and northern Africa have driven up temperatures - while it's been unusually warm in Antarctica.

A government spokesman said: "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 £11.6 billion on international climate finance and we are delivering on that pledge."