MPs have backed Boris Johnson’s cuts to foreign aid spending, despite many in his own party rebelling against the “morally reprehensible” plans.

Spending on overseas development was slashed from 0.7% to 0.5% of national income earlier this year, amounting to almost £4bn.

The cuts will be reversed only once government debt is falling and it is no longer borrowing to finance day-to-day spending – a position the UK has not been in since 1970, according to one MP.

Senior Conservative MPs, including former prime minister Theresa May, criticised the move, which goes against a direct commitment laid out in the party’s 2019 election manifesto to maintain spending.

Despite Tory rebels claiming cuts to aid would “cost lives” and critics warning of possible UK job losses as a result, MPs voted in favour by 333 to 298.

The vote was immediately condemned by leading aid agencies, with Oxfam’s chief executive saying it is a “disaster for the world’s poorest people”.

In March, openDemocracy revealed that UK contributions towards global efforts to tackle corruption and promote human rights are set to fall by as much as 80%.

British civil servants have also discussed reducing aid to Syria by two-thirds, with Libya, Somalia and South Sudan also targeted for huge aid cuts.

Speaking in the Commons today, May said: “We made a promise to the poorest people in the world, the government has broken that promise. This motion means that promise may be broken for years to come.”

It is the first time that May, an MP for 24 years, had rebelled against a three-line whip from the Conservative Party.

The former Brexit Secretary, David Davis said the cuts would “cost lives”, saying: “I consider myself an economic Thatcherite, and yet when I come to choose between money and lives, I always choose lives.

“Such a choice is morally reprehensible. Let’s be clear about it: morally reprehensible.”

Andrew Mitchell, a former international development secretary who led the Tory rebellion, told Sky News earlier today that the cuts would effectively end the UK’s spending target of 0.7% indefinitely.

“That has a huge effect on the number of avoidable deaths there will be around the world,” he said. “It has a massive impact on Britain’s international reputation and, frankly, it will have quite a strong impact on the Conservative Party, who will be seen to have broken their promise in this very important area.”

Ahead of the vote, the Universities and Colleges Union wrote to the Scottish government warning that “severe cuts threaten job losses” and called for it to “do what it can to encourage UK ministers to reverse their decisions”.

The letter, seen by openDemocracy, says that foreign aid cuts are already impacting university research projects.

Johnson today insisted that there “must inevitably be consequences” after the government’s spending to tackle the coronavirus pandemic, with the UK experiencing its deepest recession on record.

“Everyone will accept that when you’re suddenly compelled to spend £407bn on sheltering our people from an economic hurricane never experienced in living memory, there must inevitably be consequences for other areas of public spending.”

But Labour leader Keir Starmer said cutting aid “will increase costs and have a big impact on our economy”.

“Every living prime minister thinks this is wrong,” he said. “There is only one prime minister who is prepared to do this and he is sitting there.”

Starmer said that development aid reduces conflict and disease around the world, saying: “It is a false economy to pretend that this is some sort of cut that doesn’t have consequences.

“This cut will also reduce UK influence just when it is needed most, and of course it risks leaving a vacuum which other countries, for example China and Russia, will fill.”