LONDON (AFP) -- Britain on Sunday defended cuts to its aid spending, stressing the budget impact of the coronavirus pandemic, after several UN agencies warned they would translate into thousands of deaths among the world's poor.

"I've found the process of making those savings very difficult," Foreign Secretary Dominic Raab told Sky News.

"We've had to make this extremely difficult decision to reduce and find savings in the aid budget, that's because of the impact Covid has had, the biggest contraction we've seen in the economy for 300 years," he said.

Despite the cut of ?4 billion ($5.5 billion, 4.6 billion euros) to ?10 billion in its aid budget, Britain remains a leading contributor among the G7 nations, Raab added as he prepares to chair a meeting of G7 foreign ministers in London this week.

At least three UN agencies this week warned of a devastating impact after Britain informed them of steep reductions in its contributions, months after moving to suspend its legally enshrined target for aid spending. 

The children's fund UNICEF and UNAIDS added their own concern after UNFPA, the UN's sexual and reproductive health agency, said the plan would lead to some 250,000 more deaths around the world.

Raab said the government was adopting "a more strategic approach, and also to get maximum value out of every penny of taxpayers' money that goes abroad".

The G7 meeting is expected to agree on fair access to Covid-19 vaccines around the world, and is a "great opportunity ... to use our convening power and make a real team effort to tackle these problems together", he said.

Emergency pandemic support measures have sent Britain's annual borrowing rocketing to the highest level since World War II.

But Lisa Nandy, foreign affairs spokeswoman for the main opposition Labour party, said scaling back aid in the middle of the pandemic was "extraordinarily short-sighted".

"What is being cut is just appalling," she told Sky News, highlighting healthcare and scientific research. "It absolutely undermines our moral authority on the world stage."