Boris Johnson faced claims of “balancing the books on the backs of the poorest in the world” as Tory MPs condemned his cuts to aid spending.

The Prime Minister was roundly criticised by MPs of all sides for shelving his manifesto commitment to maintain spending at 0.7% of national income, instead reducing it to 0.5% – citing the economic impact of the coronavirus crisis.

But some of the fiercest and most pointed remarks came from members of his own benches, with Foreign Office minister James Cleverly sent out to defend the policy in response to an urgent question in the Commons

Conservative former international development secretary Andrew Mitchell warned the “dreadful” political decision to slash overseas aid “shames our country and our Government”.

He also insisted “red wall” voters in formerly Labour seats which helped Mr Johnson secure a commanding Commons majority also back Britain’s “life-saving” aid spending.

Mr Mitchell told the Commons: “Britain is cutting £500 million in humanitarian aid.

“That will mean that three million women and children will not now receive live-saving support – is it not clear that the original estimate of 100,000 souls who will die as a result is now a tragic underestimate?”

Conservative former prime minister Theresa May added: “The integrated review identifies the United Kingdom as a soft power superpower, citing as one of the reasons our contribution to international development.

“Exactly how is that position going to be enhanced by the action of cutting aid to the world’s poorest including those in slavery?”

Conservative Pauline Latham (Mid Derbyshire) also warned: “I am deeply saddened and very upset that we are going to be balancing the books in this country on the backs of the poorest in the world.”

She asked the Government to “come clean and be honest about where these cuts to life-saving humanitarian aid will fall”, adding: “How many women and children will die as a result? Is it more or is it less than the 100,000 estimated by the leading think-tanks and NGOs?”

Conservative former foreign secretary Jeremy Hunt questioned if Mr Cleverly was “defending the indefensible”.

Party colleague and former minister Sir Edward Leigh noted he is “no pinko leftie” but asked: “I am completely mystified from a public accounts point of view about what is going on here.”

He pointed out that the contraction of the economy would have reduced the aid budget by around £2.9 billion, but the Government is “imposing another £4 billion cut on that, we’re causing complete chaos” for aid staff in Whitehall.

For Labour, shadow international development secretary Preet Kaur Gill said: “Make no mistake, slashing humanitarian support in the middle of a global pandemic is callous and incredibly short-sighted.

“People will lose their lives as a result of the cuts and we will all be less safe. As the only G7 nation to cut aid, it is a retreat from our moral duty and will weaken our position on the world stage.”

Responding to the urgent question for the Government, Mr Cleverly said: “The simple truth is the UK economy is 11.3% smaller than it was last year and is undergoing the worst economic contraction for 300 years.”

He said the pandemic has created a “unique set of circumstances” before defending the UK’s aid spending record, insisting the country remains one of the largest donor countries in the world.

Mr Cleverly said the UK remains “absolutely committed” to spending aid cash on girls’ education, the environment and climate, plus other issues, and its diplomatic efforts will also help.

He added: “When the fiscal circumstances allow, we are committed to returning to 0.7% of GNI, which he, others and this Government are so rightly proud.”

Mr Cleverly said more details on the specific aid spending programmes will be forthcoming.