Labour leader Keir Starmer was hit by a string of resignations from his frontbench in the House of Commons on Wednesday night, after facing a rebellion from his MPs over his refusal to back a ceasefire in Gaza.
The vote calling for the ceasefire was defeated by 293 votes to 168, but eight of Starmer's frontbenchers resigned from the frontbench after supporting the amendment.
Labour MPs had been ordered to abstain on the vote and were told instead to back Starmer's position calling for longer "humanitarian pauses" rather than a ceasefire.
Starmer said he regretted that party colleagues had not backed his position, but that he wanted to be clear about where he stood.
"Much more needs to be done in this regard to ease the humanitarian crisis that is unfolding in Gaza," he said in a statement after the vote.
"Leadership is about doing the right thing. That is the least the public deserves. And the least that leadership demands."
High-profile frontbencher Jess Phillips, who was one of the most senior Labour MPs to resign, said she was quitting with a "heavy heart".
"On this occasion I must vote with my constituents, my head, and my heart which has felt as if it were breaking over the last four weeks with the horror of the situation in Israel and Palestine," she said in a letter to her party leader.
Israeli officials say about 240 people were taken to Gaza after Hamas militants stormed southern Israel on October 7 in the deadliest attack in the country's history, killing 1,200 people, mostly civilians.
The Hamas government in Gaza says Israel's ensuing aerial bombardment and ground offensive have killed 11,500 people, also mostly civilians, including thousands of children.
The row over the Starmer's stance on Israel's war with Hamas has escalated in Labour in the past week.
Starmer -- who looks set to become Britain's next prime minister at an election expected next year, according to polling -- has refused to call for a permanent ceasefire.
Instead, the former human rights lawyer has called for a humanitarian pause to Israel's bombardment to allow much-needed aid to reach ordinary Palestinians unable to leave the coastal enclave.
His stance, however, has caused disquiet within the party.
A labour spokesman said a ceasefire would freeze the conflict and "leave hostages in Gaza and Hamas with the infrastructure and capability to carry out the sort of attack we saw on October 7".
"International law must be followed at all times and innocent civilians must be protected. Labour is calling for humanitarian pauses in the fighting."