Boris Johnson is facing the prospect of a damaging Commons defeat over the government’s multi-billion pound cut to overseas aid, as a group of Conservative backbenchers launched a surprise rebellion.

Led by the former Tory cabinet minister and chief whip Andrew Mitchell, who has been rallying against the cuts, the rebel MPs said they were “confident” of having the numbers to overturn the prime minister’s healthy Commons majority.

An amendment seeking to reinstate the funds is now backed by 30 Conservative MPs, including former prime minister Theresa May, ex-ministers David Davis, Jeremy Hunt, Damian Green, Nusrat Ghani, Caroline Nokes and Johnny Mercer.

It comes amid intense criticism of the government’s decision last year to flout the Conservative general election manifesto pledge and move to slash overseas aid spending from 0.7 per cent of national income to 0.5 per cent.

Ministers have insisted the cut — estimated to be around £4 billion — is only a temporary measure due to the economic fallout of the Covid pandemic, but have refused to test support in a Commons vote, or outline any timeframe for the budget to be restored.

The risk of an embarrassing defeat for the government over its decision to cut aid for some of the poorest and unstable areas of the globe could come just days before the prime minister hosts leaders from the G7 nations, including US president Joe Biden.

Mr Mitchell has tabled an amendment to the Advanced Research and Invention Agency (Aria) Bill, a piece of legislation which establishes a new “high-risk, high-reward” research agency backed with £800 million of taxpayers’ cash to explore new ideas.

The explanatory note of the amendment says: “This new clause is intended to reaffirm the duty in the International Development (Official Development Assistance Target) Act 2015 for UK official development assistance (ODA) to amount to 0.7 per cent of gross national income each year. It will require Aria to make up any shortfall in that proportion from January 2022”.

It will be up to speaker Sir Lindsay Hoyle to decide whether the amendment is selected for consideration when the Bill returns to the Commons for further consideration on 7 June.

Mr Mitchell said: “More and more of my colleagues in the House of Commons are supporting this move to to stand by our manifesto promise.

“With our economy returning to growth, there is no justification for balancing the books on the backs of the world’s poor. With G7 leaders coming to Britain next week, there is an opportunity for us to reclaim our rightful place on the global stage.

“Britain’s national interest is not being served by the devastating impact these cuts are already having on the ground and the unnecessary loss of hundreds of thousands of innocent lives. We urge the government to think again.”

Tobias Ellwood — the Conservative chair of the Commons Defence Committee who has signed the amendment — described the government’s cut as “devastating” on BBC Radio 4’s Today programme.

Asked about the size of the rebellion, he said: “We need the number 45 [to defeat gov] and at the moment I’m confident – quietly, cautiously confident – that we’re going to get that number”. So I do hope the government will recognise where we want to go and why we want to do this.”

Opposition parties, including Labour and the Liberal Democrats, have severely criticised the cut in funding for overseas aid and are almost certain to back the amendment, if it is selected next week.

Lisa Nandy, the shadow foreign secretary, told The Independent: “As the eyes of the world turn to Britain ahead of next week’s G7 Summit in Cornwall, the government faces defeat over its short-sighted and self-defeating decision to cut foreign aid. At the very moment our international partners are stepping up to lead the global response to the pandemic, the Tories are in retreat.

“Parliament is ready to do the right thing and vote to reverse these ill-judged cuts – will the government do the same?”

Caroline Nokes — another former Tory minister backing the amendment — told ITV’s Peston programme: “It’s taken quite a lot of manoeuvring to find an opportunity to actually have a vote on this. I feel really strongly that we legislated for the 0.7 per cent commitment and the cuts are affecting women and girls.

“I am chair of the Women and Equalities Select Committee, the cuts of 85 per cent to family planning, the cuts to girls’ education – what we know from that is that if girls are not educated they won’t be empowered, they won’t be empowered if they are pregnant too early.

“Women will die because of these cuts to family planning so I have joined forces with colleagues to make sure we can have a vote on it and I will be voting to keep that 0.7 per cent.”