Boris Johnson could avoid an embarrassing defeat at the hands of his own MPs over foreign aid cuts due to a technicality.
Tory rebels are attempting to force the Prime Minister to maintain a manifesto commitment to spend 0.7% of gross national income on help for the world's poorest.
Mr Johnson decided to break his promise to voters and slash aid spending to 0.5% - a cut of around £4bn - amid the economic fallout from the coronavirus pandemic.
At least 30 Conservative rebels have backed an amendment by former International Development Secretary Andrew Mitchell which would force the Government to make up the cash cut from the foreign aid budget from a pot for a new research agency.
But they could be thwarted in their efforts if Commons Speaker Sir Lindsay Hoyle decides their amendment is not relevant to the bill.
Despite the group receiving legal advice on the plan, the clerks are understood to have expressed doubts about whether the amendment is "in scope".
A source among the rebels said the clerks had warned it was "iffy" but added: "It's up to Mr Speaker. I know he's not yet decided."
Former Tory PM Theresa May is among the senior MPs opposing the plan, alongside ex-Cabinet Ministers Mr Mitchell and David Davis.
MPs behind the plan are confident they have the numbers to overturn Mr Johnson's 80-strong majority if the amendment can be put to a vote.
Sir Lindsay will announce his decision this afternoon. His office declined to comment.
The timing of the row could not be worse for Mr Johnson as he prepares to host world leaders in Cornwall at the weekend for the G7 summit.
Mr Mitchell argued that the PM could travel to Cornwall to meet G7 counterparts like US President Joe Biden on Friday as "first among equals" if he u-turned on aid cuts.
Writing in The Guardian, he said: "The eyes of the world are truly upon us.
"But in this moment Britain is found wanting, because we have removed a foundational piece of our own global leadership.
"Britain is the only G7 nation cutting aid this year."
Ex-Brexit secretary David Davis warned that"harmful" and "devastating" cuts would result in deaths around the world.
Cuts to clean water and food for the starving will mean "thousands will die", Mr Davis told BBC Radio 4's Today programme.
He said: "No other G7 country is cutting its aid in this way. It is going to have devastating consequences across the world.
"Historically, I am a critic of aid spending, but doing it this way is really so harmful."
He added: "Morally, this is a devastating thing for us to have done."
Downing Street hinted that aid spending could exceed 0.5% of gross national income when the donation of coronavirus vaccines is taken into account.
The Prime Minister's official spokesman said: "You can expect the PM to set out more details at the G7 this week on the UK's plans to share surplus doses with developing countries.
"As is standard, any funding that benefits poverty reduction in developing countries would count as ODA (Official Development Assistance) funding."
Asked if it would be on top of the existing aid budget, the spokesman said: "The £10 billion has been largely allocated in the spending plans already set out with regards to ODA funding, but I'm not going to jump ahead of what the PM might say later this week with regards to the commitment."
Pressed if vaccine donations count as ODA spending, the spokesman said: "The £458 million we spent on Covax so far is ODA. That is factually the case."
