Cutting the UK's overseas aid budget would be morally counterproductive and damage Britain's image around the world, Ruth Davidson claimed.
The ex-Tory chief is the latest party figure to warn against any reduction in the Chancellor’s spending review on Wednesday.
Rishi Sunak has to make tough spending choices with the economy in meltdown, the pandemic still raging and the self-inflicted challenge of Brexit ahead.
Davidson, writing in The Times, said: "In a scenario where all decisions are painful ones, everything is on the table. But the suggestion that foreign aid money is directly in the firing line seems a particularly counterproductive choice - morally, economically and politically."
Sunak is reportedly planning to trim the UK's commitment to spend 0.7% of national income on overseas aid to 0.5% in the spending review.
Davidson has now joined criticism from past prime minister's David Cameron and Tony Blair.
She warned: "Politically, I can't think of worse mixed messaging to the world. 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."
Cameron, who oversaw the country first meeting the 0.7% target in 2013, said abandoning it would be a "moral, strategic and political mistake".
Blair said foreign aid – and the 0.7% target – had been a "great British soft power achievement" and that it had saved millions of lives in Africa by reducing deaths from malaria and HIV.
Last week, the Prime Minister's official spokesman drew attention to the fact the legislation enshrining the 0.7% target in UK law explicitly acknowledged it might not always be met.
Meanwhile, coronavirus has led to a strain on the public purse with the Government spending billions keeping the economy ticking over.
