A senior UN diplomat said the UK’s decision to slash its foreign aid budget is a “failure of kindness and compassion” that risks undermining its reputation abroad.
Charities including Oxfam and ActionAid UK also said the spending cut had caused "devastation" and tarnished Britain's credibility ahead of the G7 summit in Cornwall next week.
Britain is the only G7 country winding back its support for international development programmes, with the foreign aid budget slashed from 0.7 per cent of national income to 0.5 per cent.
A group of 30 rebel Conservative Party MPs, including former prime minister Theresa May, will attempt to reverse the decision on Monday in a potential vote in the House of Commons.
The group has proposed amending legislation related to a new scientific research agency to make up any shortfall from the 0.7 per cent target next year.
The Speaker of the House of Commons, Sir Lindsay Hoyle, will decide whether to allow the vote to proceed.
Ahead of the potential vote, the UN’s under-secretary-general for humanitarian affairs, Mark Lowcock, urged the government to back the MPs.
He said he was concerned the cut was undermining Britain’s trustworthiness at a crucial moment when the world is grappling with the Covid-19 pandemic.
“It is a failure of kindness and empathy. It’s a breach of a promise,” he told Times Radio.
“I’m afraid there’s no question that that costs lives. If you slash aid to starving Yemeni children, you know, they die. Likewise, in Syria.”
Mr Lowcock, who is a former head of Britain’s Department of International Development, said the UK stood alone among major economies in using the pandemic to slash aid spending.
“Every other G7 country in the world has all of these economic problems because of the pandemic,” he said.
“And nobody else is slashing their aid budget.”
Ministers have said the funding cut is needed to help improve the deteriorating budget position, with the government borrowing record amounts to respond to the pandemic.
Prime Minister Boris Johnson has promised to restore the foreign aid budget when the country’s financial situation improves but has not said when that is likely to happen.
Meanwhile, a group of charities including Oxfam, WWF UK and Save the Children warned the cuts were a “double blow to the world’s poorest communities”.
“While other G7 countries have stepped up their aid budget, the UK is the only one to have rowed back on its commitments,” the charities said.
“As a result, families are going hungry, girls are not going to school, women’s rights are being side-lined, persons with disabilities are being further left behind, vaccines are expiring on shelves, and diseases are being allowed to spread and we are reneging on our commitment to lead from the front on tackling climate change.”
Tom Tugendhat, chairman of the Commons Foreign Affairs Committee, said he was “cautiously optimistic” that MPs could defeat the government on the cuts.
“We’re trying to make sure Britain’s foreign footprint - Global Britain - really means something,” he told Sky News.
“The reality is that Britain has a huge opportunity to shape the world in extraordinary flux. This, along with our defence, diplomatic and trade capabilities, is part of that.”
Health Secretary Matt Hancock told the BBC on Sunday that the “temporary” spending cut was "entirely reasonable", given that the pandemic had caused a "once-in-300-year economic interruption".
UN Secretary- General Antonio Guterres previously described the cuts as a "death sentence".
The reduction in spending led to UK aid to Yemen being cut from £197m pledged in 2020 to £87m this year.
Funding for the Global Polio Eradication Initiative was reduced from £100m to £5m, while education funding for girls was cut by 40 per cent on average from the previous four years.
The UN Population Fund said the UK planned to cut family planning aid from £154 million to £23m this year.