The suspension of funding by countries including the UK and US followed allegations UNRWA staff were involved in the 7 October Hamas attacks on Israel.

"These decisions threaten our ongoing humanitarian work across the region including and especially in the Gaza Strip," commissioner general Philippe Lazzarini said.

Follow live: 'Ironclad' intel shows UN agency staff links to Hamas

"UNRWA is the primary humanitarian agency in Gaza, with over two million people depending on it for their sheer survival," Mr Lazzarini said.

"Some 3,000 core staff out of 13,000 in Gaza continue to report to work, giving their communities a lifeline which can collapse anytime now due to lack of funding," he added.

He suggested UNRWA would be "forced to suspend its humanitarian response" if funding was not reinstated.

On Friday the agency said it had opened an investigation into several employees and severed ties with those people.

In the wake of the allegations, the Foreign Office said it was "temporarily pausing any future funding of UNRWA whilst we review these concerning allegations".

It said it was "appalled" by the claims, adding: "We remain committed to getting humanitarian aid to the people in Gaza who desperately need it."

'Just the tip of the iceberg', senior adviser to Israeli PM says

It comes after a senior adviser to Israeli Prime Minister Benjamin Netanyahu said there was "documented, clear and ironclad" information showing 12 UNRWA staff members were part of the Hamas force that broke into Israel and killed 1,200 civilians.

Mark Regev said a lot of the information that led to the accusations was shared by Hamas on social media.

"Hamas went live on social media and boasted a lot of the material, so you actually see the faces and the people involved in a lot of the crimes," he told Sky News.

Mr Regev added the alleged UNRWA staff involvement in Hamas's operations was "not an aberration" and that this investigation was "just the tip of the iceberg".

Israeli Foreign Minister Israel Katz has said UNRWA should be replaced once fighting in the enclave dies down.