He added that some in the party had "allowed their passion to run away" and expressed themselves in "a light which could be perceived as antisemitic... I don't believe they are antisemites."
JLM chair Ivor Caplin wrote to Chief Whip Nick Brown on Thursday to say Mr Williamson has shown “no contrition or attempt to educate himself".
“It is clear that Mr Williamson believes, contrary to Labour’s entire leadership, that there is no antisemtisim in our party, and that it’s all a smear, which in itself draws upon antisemitic tropes," Mr Caplin wrote.
“To be silent in the face of antisemitism is to be complicit.”
Mr Caplin said it was JLM’s “firm belief that the Labour whip should be suspended [from Mr Williamson] indefinitely.
“Holding the Labour whip is a privilege, not a right, and comes with expectations regarding behaviour.”
Mr Caplin said Mr Williamson has not learned anything about Jew-hate within Labour despite meeting JLM in October of last year, in an attempt to educate him about the problem.
“He was presented with examples, fully explained the pervasive and widespread antisemitism that stains our party and appeared to show contrition for his remarks. His actions since then prove this to not be the case,” Mr Caplin wrote.
“JLM believe that he has already been warned regarding his behaviour, which, to date, includes repeatedly sharing platforms with expelled and suspended members of the Labour Party, claimed those speaking out against antisemitism within our Party were Tories in disguise, and regularly denying that antisemitism exists within Labour.”
There were previous calls to suspend Mr Williamson after he shared a platform with Marc Wadsworth, the party activist who was expelled after he haruanged Jewish Labour MP Ruth Smeeth at the 2016 launch of the Chakrabarti Report into Jew-hate within Labour.
The JC can reveal that another pro-Corbyn MP, Dan Carden, backed Mr Williamson at Tuesday's Momentum meeting - despite reassuring representatives from the Jewish Leadership Council the previous week that he was committed to the fight to rid the party of antisemitism.
Mr Carden, the MP for Liverpool Walton, and a former assistant of Unite the Union chief Len McCluskey, told the meeting: "I'd like to welcome Chris Williamson who is a great comrade to have down in Westminster when you are fighting for what we are fighting for which is a socialist government.
"To have comrades like Chris who say it like it is is an absolute pleasure and privilege."
