Millions of Palestinian refugees have been placed in 'serious jeopardy', a spokesman for one of the UK's largest Christian relief organisations said on Monday, hitting back at a US aid cutoff.

There are around 5 million Palestinian refugees across Jordan, Lebanon, Syria and the West Bank and Gaza. Most are descendants of some 700,000 Palestinians who were driven out of their homes or fled fighting in the 1948 war that led to Israel's creation.

The growing refugee count was cited by Washington in its decision last week to withhold funding from the United Nations Relief and Works Agency (UNRWA), and has potential ramifications for the Palestinians' pursuit of a right of return to land now in Israel.

Successive Israeli governments have ruled out such an influx, fearing the country would lose its Jewish majority.

Christian Aid's spokesman William Bell said the US 'cannot present itself as an impartial peace broker between Israel and the Palestinians' as a result. 'The primary motive appears to be to challenge the number of eligible Palestinian refugees who can claim the right of return to their former homes in what is now Israel and the occupied Palestinian territory. With one stroke, the status of millions of Palestinian refugees and the humanitarian lifeline they depend upon for vital health, social and education services is in serious jeopardy,' he said.

'Such a move will clearly send shockwaves through a population who have endured 70 years of vulnerability and insecurity throughout the Middle East, including Syria.'

He stressed Christian Aid's support for Israel's right to a secure and peaceful existence, but said: 'We cannot stand by and watch as Palestinian lives are consistently treated as second class.'

'By threatening the vital humanitarian services that UNRWA provides and challenging people's identity, the US is condemning millions to even greater insecurity. A peace process is not a blunt instrument to bend people against their will. It must be the path that leads all to security, prosperity and hope,' he concluded.

UNRWA Commissioner-General Pierre Krahenbuhl said in an open letter to Palestinian refugees and the agency's staff: 'I express deep regret and disappointment at the nature of the US decision.'

However, appearing to echo Israel's view that descendants of the 1948 refugees should not share that status, State Department spokeswoman Heather Nauert criticised UNRWA on Friday over its 'endlessly and exponentially expanding community of entitled beneficiaries'.

Israeli Prime Minister Benjamin Netanyahu described UNRWA on Sunday as 'the refugee perpetuation agency' whose money 'should be taken and be used to really help rehabilitate the refugees, whose real number is a sliver of that reported by UNRWA'.

But Krahenbuhl said 'the protracted nature of the Palestine refugee crisis' was not unique. He said the children and grandchildren of long-displaced refugees in Afghanistan, Sudan, Somalia, Congo and elsewhere are also recognised as refugees and assisted by the United Nations.

Schools open

'No matter how often attempts are made to minimise or delegitimise the individual and collective experiences of Palestine refugees, the undeniable fact remains that they have rights under international law and represent a community of 5.4 million men, women and children who cannot simply be wished away,' he said.

The United States paid out $60 million (£46.5 million) to UNRWA in January, withholding another $65 million, from a promised $365 million for the year. Krahenbuhl said Gulf states had injected funds but UNRWA still needed more than $200 million.

In Lebanon on Monday, UNRWA opened its school year as scheduled. Studies in UNRWA-run schools in the occupied West Bank and the Gaza Strip got under way on Wednesday.

Claudio Cordone, director of UNRWA Affairs in Lebanon, told Reuters that funds would last only until the end of the month but the agency would continue to raise money to ensure the schools remain open.

Washington's move against UNRWA was the latest in a series of US and Israeli policy decisions that have angered Palestinians and raised international concern.

They include Trump's recognition of Jerusalem as Israel's capital in December, the moving of the US Embassy to the contested city in May and Israel's adoption of a 'nation-state' law in July that says only Jews have the right of self-determination in the country.

Additional reporting by Reuters.