The UK backed a United Nations Security Council (UNSC) call for a ceasefire in Gaza during the Muslim holy month of Ramadan.
Downing Street said the UNSC resolution sent a clear message that the hostages held by Hamas should be released and aid should allowed in to Gaza.
The Prime Minister’s official spokesman said Israel had a right to defend itself but too many Palestinian lives were being lost, with a “clear and present risk” of a humanitarian catastrophe in Gaza.
Israel’s ally the US did not wield its veto at the Security Council and the resolution is the first time the body has called for a halt to the fighting.
The resolution did not link the demand for a release of the hostages to the ceasefire during Ramadan, which runs until April 9.
It is hoped a pause in the fighting could lead to a sustainable ceasefire, with the UK saying a lasting peace would mean Hamas being ousted from power in Gaza and not being in a position to launch attacks against Israel.
The Prime Minister’s official spokesman told reporters: “We have long called for an immediate humanitarian pause or temporary ceasefire leading to a sustainable ceasefire, which is what this resolution calls for.
“And that is why the UK voted in favour of it.
“We of course recognise that Israel continues to deal with the aftermath of the brutal attacks on October 7 and innocent hostages continue to be held by Hamas.
“Israel has a right to defend itself and ensure that such an attack can never happen again.”
But “far too many” Palestinians had been killed “and a humanitarian catastrophe is a clear and present risk”.
“This resolution sends a clear message for the need for all hostages to be released and for aid to be scaled up,” the spokesman added.
Asked what message the Government would send to Israeli prime minister Benjamin Netanyahu, the official said: “We would obviously urge both sides to listen to that and to follow this resolution.”
Challenged over whether the UN vote would make any difference, the spokesman said: “We’ve obviously seen a number of talks in recent weeks and we believe and have previously said that we hope negotiators can reach an agreement on a temporary ceasefire as soon as possible.”
Mr Netanyahu’s immediate response to the UN resolution was to cancel a planned visit to Washington by a high-level delegation in protest.
He accused the US of “retreating” from what he said had been a “principled position” by allowing the vote to pass without linking the ceasefire to the release of the hostages held by Hamas.
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