Rishi Sunak’s bid to cut foreign aid could be thwarted in Parliament as it emerged that legislation may be required to enable the £4 billion reduction to go ahead.
On Tuesday night, senior Tories warned the Government would have “serious problems” forcing through the planned reduction of the target from 0.7 per cent of national income to 0.5 per cent.
Mr Sunak is expected to confirm the 12-month cut in Wednesday’s comprehensive spending review, arguing that a brief cut to overseas aid is justified at a time of severe economic hardship at home.
However, while exemptions in the International Development Act allow the Government to miss the target in certain circumstances, critics argue that these can only apply retrospectively.
It means that Dominic Raab, the Foreign Secretary, who is the minister responsible for the commitment, could face a legal challenge if the Government seeks to declare in advance that it intends to miss the target.
Whitehall sources confirmed that the Treasury had asked lawyers to assess whether legislation may now be required in order to prevent the cut being judicially reviewed.
The Telegraph understands that the Chancellor has also privately conceded that MPs may have to be given a vote.
The disclosure prompted a last-ditch attempt by moderate one nation Tories to try and persuade Boris Johnson to shelve the plan, warning that he would face a major backbench rebellion if it needed approval in Parliament.
Speaking to The Telegraph on Tuesday night, Damian Green, chairman of the One Nation Caucus of MPs, said that dozens of Conservative MPs could defy the whip if the cut was put to a vote.
While Mr Johnson commands a majority of 80 in the House of Commons, the One Nation Caucus makes up approximately one third of the Parliamentary party – more than enough to overturn it.
“If the Government tries to pass a law effectively repealing the current obligations on aid they will have severe problems getting it through the House of Commons,” Mr Green said.
“There is a lot of unease across the Conservative Party about breaking manifesto commitments. I know dozens of my colleagues will be wary of supporting that.”
His comments were echoed by Andrew Mitchell, a former international development secretary, who said: “Many of us are very sympathetic to the Chancellor and want to give him strong support.
“But the 0.7 target is a promise to the poorest in the world, quite apart from being a manifesto commitment at the last election.
“At a time when we are about to assume the chair of the G7 it doesn’t make sense to trash our own reputation.”
It comes after Ruth Davidson, the former Scottish Conservative leader, became the latest figure to criticise the move, arguing that it was a "counterproductive choice – morally, economically and politically".
Writing for The Times, Ms Davidson added that any “plaudits” would go to Mr Sunak, while the Prime Minister would be forced to endure the backlash from other world leaders and the international community.
“He knows that 80 is only a big majority until 40 MPs refuse to balance the books off the back of the world’s poor, emboldened by a House of Lords that feels no compulsion to wave this through as it directly contradicts the Government’s mandate,” she added.
Dozens of charities, church leaders, former heads of the armed forces and Bill Gates, the billionaire philanthropist, have also urged Mr Johnson to reconsider.
Staging a joint intervention last week, David Cameron and Tony Blair told The Telegraph that Mr Johnson was at risk of jeopardising Britain's "soft power" status on the global stage.
Activist Malala Yousafzai tweeted: "COVID-19 could force 20 million more girls out of school. To keep girls learning, we need leaders to prioritise education. @BorisJohnson & @RishiSunak: the U.K. pledged 0.7% in aid last year. When you announce spending priorities tomorrow, I hope you'll deliver on that promise."