Boris Johnson on Tuesday fended off a rebellion by senior Conservatives — led by former premier Theresa May — to win MPs’ backing for cuts to Britain’s overseas aid spending.

After bitter accusations from senior Tories that Johnson was trying to balance the books on the backs of the world’s poor, the government won a vote on the £4bn aid cut by 333 to 298, a majority of 35.

Theresa May voted against her party for the first time in a 24-year career as an MP, accusing the prime minister of breaking a manifesto promise on overseas aid that would last “for years to come”.

Sir John Major, the former Tory prime minister, said in a statement: “The Government has blatantly broken its word, and should be ashamed of its decision.

“It seems that we can afford a ‘national yacht’ that no one either wants or needs, whilst cutting help to some of the most miserable and destitute people in the world. This is not a Conservatism that I recognise. It is the stamp of Little England, not Great Britain.”

Johnson insisted that the cut to overseas aid was only “temporary”, but forecasters predict the savings are likely to continue until at least the end of this parliament.

May, prime minister from 2016-19, accused the government of “turning its back on the poorest in the world” by suspending its target of spending 0.7 per cent of gross national income (GNI) on overseas aid.

“Fewer girls will be educated, more girls and boys will become slaves, more children will go hungry, and more of the poorest people in the world will die,” she said.

Andrew Mitchell, former Tory international development secretary, said “an unpleasant odour is wafting out from under our party’s front door” and that the affair was alarming liberal, internationalist voters.

But potential Tory rebels were given political cover to back the government after chancellor Rishi Sunak published a formula under which current aid spending of 0.5 per cent of GNI would return to 0.7 per cent.

Sunak said on Monday the government would reverse the cut once the UK was no longer borrowing to fund day-to-day spending and once underlying debt was falling as a share of gross domestic product.

On current predictions by the Office for Budget Responsibility, the fiscal watchdog, those tests will not both be met until 2025-26, although the OBR forecasts could change.

Mitchell said the new formula — and its acceptance by some potential rebel Tory MPs — was “a tribute to the chancellor’s silver tongue”, but he added: “It is a fiscal trap for the unwary.”

He added that the dual conditions set out by Sunak to restore the 0.7 per cent aid target had only been met once in the past 20 years. May said: “I certainly doubt if the tests will be met in five years’ time.”

Rachel Reeves, Labour’s shadow chancellor, said the formula was intended to ensure that the 0.7 per cent target would “never be met again” under a Conservative government.

The decision to cut aid spending has been criticised by May and every other living former prime minister but Johnson insisted it was evidence of the “wrenching” choices forced on the government by the Covid-19 crisis.

Johnson insisted it would be a “travesty” to suggest that Britain was retreating from its position as a major international aid donor, adding that every pound spent on aid was having to be borrowed.

The prime minister argued that since Britain’s overall debt is “climbing towards 100 per cent of GDP” and that annual borrowing was almost £300bn, the government had to make hard choices.

The issue inflamed passions on the Tory benches. Some Conservatives argued that the decision was correct, noting also that many voters dislike the government spending so much money in the developing world.

Others, including May, said that Tuesday’s House of Commons vote came in spite of the fact that all 650 MPs from all parties in the Commons stood at the last election committed to upholding the 0.7 per cent overseas aid target.