The Archbishop of Canterbury has attacked the Government for its “shameful and wrong” cuts to the foreign aid budget, as Boris Johnson faced intense criticism for reversing one of the pledges in his election manifesto.

Chancellor Rishi Sunak announced the overseas aid budget will be cut to 0.5% of gross national income in 2021, adding that the Government’s “intention” was to return to 0.7% when the fiscal situation allows.

The decision prompted a fierce backlash, including from Justin Welby, who tweeted: “The cut in the aid budget – made worse by no set date for restoration – is shameful and wrong. It’s contrary to numerous Government promises and its manifesto.

“I join others in urging MPs to reject it for the good of the poorest, and the UK’s own reputation and interest,” he added.

Oxfam chief executive Danny Sriskandarajah said: “Cutting the UK’s lifeline to the world’s poorest communities in the midst of a global pandemic will lead to tens of thousands of otherwise preventable deaths.”

Highlighting the Government’s announcement of an increase in spending on defence, Mr Sriskandarajah added: “At a time when hundreds of millions of people are hungry and decades of progress against poverty is under threat, today’s decision is a false economy which diverts money for clean water and medicines to pay for bombs and bullets.”

The criticism follows interventions ahead of the statement from former prime ministers Sir John Major, David Cameron and Tony Blair, as well as Nobel Prize laureate Malala Yousafzai.

Sir John told The Times: “Cutting our overseas aid is morally wrong and politically unwise. It breaks our word and damages our soft power.

“Above all, it will hurt many of the poorest people in the world.

“I cannot and do not support it.”

The 0.7% target is written into law and Mr Johnson’s 2019 election manifesto promised to keep it.