Sir Keir Starmer has written to Labour councillors, following a number of resignations over his stance on the Middle East crisis.
The Labour leader has repeatedly insisted Israel has a right to defend itself, within international law.
But his comments in a radio interview last week have sparked anger among some Labour activists.
In an interview on LBC radio last week, Sir Keir said Israel had the “right to defend herself” after Palestinian militant group Hamas launched unprecedented attack on 7 October that killed 1,400 people.
He added that this included “everything it can” to get hostages taken into Gaza home “safe and sound”.
Pressed on whether cutting off water and power supplies into Gaza would be appropriate as part of an Israeli response, he replied: “I think that Israel does have that right, it is an ongoing situation.
“Obviously, everything should be done within international law, but I don’t want to step away from the core principles that Israel has a right to defend herself”.
Some Labour councillors quit the party over Sir Keir’s comments, which they argue amounted to an endorsement of the collective punishment of Palestinian people, against international law.
But Sir Keir’s spokesman sought to defuse the row on Wednesday – a week after the interview was broadcast – by suggesting the Labour leader had only meant to say Israel had a general right to self-defence.
So far, about a dozen Labour councillors – out of more than 6,000 – are reported to have resigned over Sir Keir’s stance.
Two of them, Shaista Aziz and Amar Latif, who sit on Oxford City Council, said Sir Keir’s remarks seemed “to condone the use of collective punishment against the people of Gaza in direct contravention of international law”.
But speaking to reporters on Wednesday, Sir Keir’s spokesman said his answer that Israel had “that right” referred only to the general right to defend itself.
He added that there “overlapping questions and answers” during the LBC interview, and the Labour leader had been “consistent” in all his interviews that Israel should follow international law.
The Labour leader has also written to all of the party’s councillors, adding they had a role in ensuring its stance is “communicated to constituents” in their local areas.
In the letter, first reported by the New Statesman, Sir Keir said there should be “humanitarian corridors and humanitarian access, including food, water, electricity and medicines” to people in Gaza – as well as protection for aid workers.
Video call
“Labour has been clear; Israel has the right to defend herself; to keep its people safe and bring hostages home,” he wrote, adding this must be “conducted in accordance with international law”.
It comes after Sir Keir’s chief of staff Sue Gray and David Lammy, Labour’s shadow foreign secretary, held a video call on Monday evening to discuss the party’s response.
Sources said the call was an opportunity for councillors to “air their views” – but the party would not be changing its position as a result of the meeting.
Some on the left of the party have joined the SNP in calling on Sir Keir, as well as the government, to back a ceasefire to protect civilians.
However the Labour leader, like Prime Minister Rishi Sunak, has declined to back the call and reiterated their support for Israel’s right to self-defence.
Sir Keir has sought to present a united front with the government over the conflict, arguing that political division would aid the “enemies of peace and democracy”.
On Wednesday, Foreign Secretary James Cleverly told MPs he had seen “absolutely nothing” to suggest Hamas would respect a ceasefire.
