Blogger Daniel Margrain, who was once defended by Barnet Momentum members after he was refused Labour membership over a blog about "the over-representation of Jews in the capitalist ruling class", tweeted: "We are not supposed to say this, but I'm going to say it anyway..
"Might I suggest that Lansman is motivated by a sense of tribal affinity in relation to his defense of the indefensible. There I've said it."
Tweeter Diana Neslen attacked Mr Lansman's objection to Stephen Marks, a JVL activist who was included on a list of candidates to be voted onto Labour''s highest disciplinary body, despite the fact he once accused the Board of Deputies of being behind “imagined” claims of antisemitism in the party.
She wrote: "So it gives those who believe in 'the centrality of Israel in Jewish life' an effective veto over the left in the Labour party."
The JC has learned that Ms Neslen, a Labour member who had once defended Ken Livingstone over his Hitler and Zionism remarks, had previously been reminded of the conduct expected from a Party member after a complaint about her conduct.
One Twitter account calling itself "Rozalia Luxenburg", wrote: "Lansman behaves as if he is paid by the Israel lobby in the UK - and he probably is."
A further message written a known pro-Corbyn Twitter account, named Coo1 Daddy, said: "Lansman is a Zionist who does support left wing domestic policies but his loyalty to Apartheid Israel has got in his way for him to be an honest broker and hence is a liability."
Bitter factional rivalries erupted among the Labour left after Momentum issued a statement suggesting they would not back the inclusion Mr Marks on a list of six candidates to be elected onto Labour's national contistutional committee (NCC).
There were claims Mr Lansman had suggested Mr Marks would not acceptable to the "Jewish community."
But this put Mr Lansman at odds with the Campaign For Labour Democracy group - led by Pete Willsman, whom the JC exposed when it published the audio of his rant about Jewish 'Trump fanatics' at a Labour meeting.
Mr Willsman favoured Mr Marks' inclusion on the left wing slate.
In a bid to stop a full-on left-wing split, last week Mr Lansman relented and agreed to allow Mr Marks to be included on the list.
But last week the JC revealed Mr Lansman had privately admitted he viewed JVL's existence as a problem, inflaming tensions between Labour and the Jewish community.
The JC has also learned that Mr Lansman accepts that some of the abuse he has received in recent weeks has been of an antisemitic nature.
But he has told friends that he feels the abuse he receives pales into significance when compared to that directed at Jewish Labour MP such as Ms Berger.
In an effort to explain his support for the state of Israel, Mr Lansman tweeted on Monday that he believed "we are now in a post-Zionist age."
He added: "You don’t have to be a Zionist to support the existence of Israel, and you don’t have to be an anti-Zionist to support Palestinian rights and statehood or equality for all who live between the Jordan and the sea."
