Sir Keir Starmer has said he "stands by" his decision to sack shadow minister Rebecca Long-Bailey after a meeting with left-wing Labour MPs.
The Labour leader said the virtual meeting was "constructive" but his mind was "made up" on the matter.
The MPs had urged him to reinstate Mrs Long-Bailey as shadow education secretary.
Mrs Long-Bailey was sacked after sharing a story Sir Keir said contained an anti-Semitic conspiracy theory.
During the Zoom meeting, Sir Keir spoke to more than 20 MPs in the Socialist Campaign Group, who have expressed concern about Mrs Long-Bailey's removal as shadow education secretary on Thursday.
Its membership includes former leader Jeremy Corbyn and other prominent left-wingers such as Diane Abbott and Richard Burgon, although the list of MPs that took part has not been released.
Campaign Group MPs who took part said they wanted reassurance that those who criticised the Israeli government would not be suspended.
The meeting had happened "in a mutually respectful manner" and there had been a "significant disagreement", the MPs said in a statement.
They received assurances that no further disciplinary action against Mrs Long-Bailey was being sought but Sir Keir rejected calls for her reinstatement.
Sir Keir said: "We engaged in, for about an hour, a discussion but my mind is made up on this. I took my decision yesterday and put out my statement yesterday."
He sacked Mrs Long-Bailey, MP for Salford and Eccles, from his frontbench team on Thursday after she tweeted that actress and Labour supporter Maxine Peake was "an absolute diamond", adding a link to an interview with her on the Independent website.
In the article Ms Peake suggested US police learned violent tactics from Israeli secret services - a claim she subsequently described as "inaccurate".
After her sacking, Mrs Long-Bailey said she did not agree with all aspects of the article and it had not been her "intention to endorse every part" of it.
Jewish groups and some MPs welcomed Sir Keir's decision but Mrs Long-Bailey's allies on the party's left said it had been an overreaction.
At Friday's meeting with Sir Keir, Socialist Campaign Group members said there was "a need" for MPs and others within Labour to speak out against the Israeli government ahead of moves to annex parts of the occupied West Bank.
BBC political correspondent Iain Watson says he was told there was "some" understanding of Sir Keir's position, with a damning report from the Equality and Human Rights Commission on anti-Semitism in the party expected soon, and that he had to be seen to be acting decisively.
Labour has struggled with allegations of anti-Semitism since 2016.
It became a constant backdrop to the tenure of former Labour leader Jeremy Corbyn and Sir Keir stood as his successor on a platform of being tough on anti-Semitism in the party.
A reopening of divisions?
In demonstrating firm leadership, Sir Keir Starmer has inevitably highlighted his party's divisions.
The sacking of Rebecca Long-Bailey brought plaudits from MPs who had been close to ex-party leaders Tony Blair and Gordon Brown and from the Jewish labour movement.
But it attracted denunciation from those who had most strongly supported Jeremy Corbyn
Some don't believe Maxine Peake's assertion - that the American police had learned the technique that killed George Floyd from the Israeli security services - was anti-Semitic. But in any case Mrs Long-Bailey hadn't specifically endorsed this and Peake had admitted she'd been wrong.
So they will question whether Sir Keir was looking for an excuse to marginalise the left.
Momentum has begun a petition against the sacking and is urging members to win back power within the party.
Sir Keir's allies say the sacking of Mrs Long-Bailey should be taken at face value - she had refused to take down her retweet of Peake's views.
And that when he promised Jewish community groups "actions not words" on anti-Semitism, he had to deliver.
The removal of Mrs Long-Bailey was not part of a grand plan, they said, and it was "nonsense" that he was simply seeking an excuse to fire her.