John Major has thrown his weight behind efforts to overturn government cuts to the UK’s overseas aid. Ahead of a possible Commons vote on the issue next week, the former prime minister said the UK needed to remain “a nation that keeps its word”. In a brief but strongly worded statement, Major said he had made his views known to ministers in private some weeks ago. “Even at this late hour I hope they will honour their better instincts and let compassion prevail to aid those in dire need,” he said. His intervention comes a day after another Conservative former PM, Theresa May, joined a revolt which is seeking to reverse a cut in the overseas aid budget from 0.7% of GDP to 0.5%, justified by Boris Johnson’s government on economic grounds. The rebellion centres on an amendment to the advanced research and invention agency bill, which has its report stage in the House of Commons on Monday, introducing a new clause reversing the cuts. Thirty Tory MPs plan to sign the amendment, and with 40 needed to defeat the government if the amendment is selected for a vote, those leading the rebellion are confident they will have enough support. Major said in his statement: “Whilst I fully recognise our own budgeting difficulties, I do not believe it is morally defensible to ease our own financial burden at the expense of some of the poorest and most vulnerable people in the world, who have nothing – and nowhere else to turn for help.” Only a reversal to the policy would mean the UK could “re-establish ourselves as a nation that keeps its word, and begin to repair our reputation as a global force for good”, he said. Every living former prime minister is opposed to the plans. David Cameron, Tony Blair and Gordon Brown have already expressed their dissent. The Commons amendment is in the name of the former international development secretary Andrew Mitchell and the former Foreign Office adviser and newly elected MP Anthony Mangnall. Sources say organisers behind the move have had enough assurances from other MPs to meet the threshold for victory, with more names expected to be revealed over the weekend. Ministers have billed the cut, which will mean a reduction in aid spending of about £5bn, as a temporary measure caused by the economic damage from Covid. As such, they argue, it does not require a Commons vote, despite the 0.7% target being in the Tories’ 2019 election manifesto.