A Nobel Peace Prize winner and Ruth Davidson have begged Boris Johnson and Rishi Sunak not to cut the overseas aid budget in tomorrow's UK spending review.

The Chancellor is widely expected to reduce the UK’s commitment to spend 0.7% of national income on overseas aid tomorrow.

Indian Nobel laureate Kailash Satyarthi — who was honoured for his work on children's rights — told the Prime Minister the rumoured reduction would be “immoral and dangerous”.

And former Scottish Conservative leader Davidson called the anticipated reduction to 0.5% a “counterproductive choice – morally, economically and politically”.

In a letter to Johnson, Satyarthi, who won the Nobel Peace Prize six years ago, told Johnson: “This year the world has faced a common enemy like never before, yet the response so far has been to look after the richest and leave the poorest to fend for themselves.

“History will judge this harshly and it will be unforgivable if leaders now cut one of the few sources of support for the most marginalised.

“Such a cut would exemplify the gross inequality that is starting to define our times; it is difficult to imagine anything more inhumane.”

Writing separately in The Times newspaper, Davidson — who will next year enter the House of Lords — said the cut could be seen as “mixed messaging” to the world.

She wrote: “Barely a week after a big defence announcement, arguing that ‘Global Britain’ had been in retreat for too long and pledging to better shoulder our global defence responsibilities, that same ‘Global Britain’ turns around and says we’ll walk away from our humanitarian and development ones.”

The MSP joins former prime ministers David Cameron and Tony Blair in warning against the move, while Archbishop of Canterbury Justin Welby has also made a significant intervention.

The 0.7% target is written into law and Johnson’s 2019 election manifesto promised to keep it.

The Prime Minister’s official spokesman would not confirm the expected cut but said Johnson had stressed that “the people of this country should be proud of the support we give around the world”.

The aide said: “The UK is and will remain one of the biggest contributors of aid of any country.

“But, as we have said, it is important to look at where savings can be made and to ensure that aid spending is used effectively.”