Senior party figures - including some frontbenchers - want their leader to call for an immediate end to hostilities so that vital humanitarian aid can reach civilians in Gaza.
More than 150 Muslim Labour councillors also signed a letter today calling on the party leadership to back a ceasefire.
Starmer is also under fire for an interview he gave to LBC in which he appeared to support Israel in turning off supplies of water, power and food to the region in the wake of Hamas’ terror attacks on Israel nearly three weeks ago.
The Labour leader met with around a dozen Muslim Labour MPs at lunchtime today to hear their concerns amid reports that two members of the shadow cabinet could resign over the row.
Sources close to Starmer said the meeting had been “constructive” and that he will continue to meet with party members to hear their concerns.
But in a statement, the Labour leader would only say he backs US Secretary of State Antony Blinken’s call for “humanitarian pauses” in the fighting to let aid to Gaza get through.
Starmer said: “It’s clear that the amount of aid and essential utilities getting into Gaza is completely insufficient to meet the humanitarian emergency on the ground.
“That’s why we have repeatedly said that aid, fuel, water, electricity and medicines must be urgently ramped up both through what can come in through the Rafah crossing and through Israel turning back on the supplies it controls.
“It is incumbent on all parties to make sure that the aid and utilities don’t just get in but reach those who need them. That’s why we’ve said deliveries need to be regular, fast and safe. We welcome Secretary Blinken’s comments last night and we support humanitarian pauses.
“In the long term there can only be a political solution to this crisis which is why we need to restart the hard work of talks for a two-state solution of a viable Palestinian state alongside a safe and secure Israel.”
One Starmer ally told HuffPost UK that there was no point demanding a ceasefire that “neither Israel or Hamas is interested in”.
“The problem is that some are using it to undermine Keir which in itself is disgraceful given the gravity of this issue,” he added.
In a further sign of the tensions within Labour on the issue, shadow equalities minister Yasmin Qureshi departed from the party’s official line on a ceasefire during prime minister’s questions.
She asked: “How many more innocent Palestinians must die before this prime minister calls for humanitarian ceasefire?”
A spokesman for Starmer would not say whether Qureshi would be disciplined for her comments.
Scottish Labour leader Anas Sarwar has also accused Israel of a “clear breach of international law” - something Starmer has refused to do.
The Labour leader’s spokesman said: “Anas is entitled to his views on this.”
Starmer has also seen at least 19 Labour councillors quit the party over the issue.