More than 100 organisations have joined forces to condemn the shock move as “a betrayal” and “a death sentence” for millions of people in desperate need.
They also say the prime minister has badly misjudged the national mood if they believe the cut – the start of a £4bn-a-year reduction from the aid budget – will have public support.
“History will not judge this nation kindly if the government chooses to step away from the people in Yemen and thus destroy the UK’s global reputation as a country that steps up to help those most in need.”
The protest comes as similar cuts to a swathe of the world’s other poorest countries are revealed, to start within weeks – as MPs are denied a promised vote on the controversy.
Syria, Somalia, the Democratic Republic of Congo, Libya, Nigeria and Lebanon are all poised to lose more than half of their funding, according to information seen by The Independent.
MPs had made repeated attempts to obtain the details of the cuts planned, but were rebuffed by the Foreign, Commonwealth and Development Office (FCDO).
“Slashing aid to Yemen – a country on the brink of famine – is a betrayal of Britain’s claim to global leadership and of British values,” said Danny Sriskandarajah, Oxfam’s chief executive.
“Aid cuts are a false economy that will remove a vital lifeline from millions of people in Yemen and beyond who can’t feed their families, have lost their homes and whose lives are threatened by conflict and Covid.”
And Laurie Lee, chief executive of Care International, said: “The government must reverse this decision urgently before more lives are lost.”
It is the first stark impact of the controversial decision to cut spending on international aid from 0.7 to 0.5 per cent of national income.
Dominic Raab, the foreign secretary, had promised legislation – admitting the move could be unlawful without it – but a vote was shelved and may now not take place at all.
Until last night, only the Yemen cut had been revealed – a reduction to £87m, from £197m last year – and only because an international donor conference was staged.
Criticised by Sir Keir Starmer in the Commons, Mr Johnson drew fresh condemnation for saying Labour should not be focusing “on the interests of the people of Yemen”.