Haltemprice and Howden MP David Davis is one of 30 Tory MPs preparing to rebel next week in a bid to force Boris Johnson to reverse his widely-criticised cuts to foreign aid.
Former prime minister Theresa May is also among those heaping pressure on the Prime Minister to avert a Commons revolt as the number of Tory MPs to back a rebel amendment doubled from 15 overnight.
Mrs May's former deputy Damian Green and Johnny Mercer, who recently resigned as defence minister, also added their names to an amendment led by former international development secretary Andrew Mitchell.
Mr Johnson has been criticised across the political spectrum for temporarily reducing foreign aid from 0.7% of national income to 0.5%, breaking a manifesto commitment.
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 amendment, if selected by Commons Speaker Sir Lindsay Hoyle and approved by a majority of MPs, would force any shortfall of the 0.7% foreign aid spending target to be made up by Aria's budget.
Mr Davis, a former Brexit Secretary, wrote on Twitter: "The 0.7 per cent foreign aid spending pledge was a manifesto commitment.
"In providing aid to the world's poorest countries, we save lives and reduce crippling poverty. If the government wants a truly global Britain, we must meet our international promises."
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."
The Government has blamed economic damage caused by the Covid-19 pandemic for its aid decision.
But critics in the aid sector have warned it will result in tens of thousands of deaths in other parts of the world.
Senior Conservatives to back the amendment include former health secretary Jeremy Hunt and former Welsh secretary Stephen Crabb, as well as father of the House Sir Peter Bottomley.
Others include select committee chairs such as Caroline Nokes, Tom Tugendhat, Karen Bradley and Tobias Ellwood.
The amendment is also collecting support from the Labour benches, with signatories so far including International Development Committee chair Sarah Champion and Public Accounts Committee chair Meg Hillier.
The Bill returns to the Commons for further consideration on Monday.