Momentum founder Jon Lansman has been attacked for “Jewish exceptionalism” by the partner of a senior figure in the Jewish Voice For Labour group.

Jackie Walker – previously expelled by Labour for “grossly detrimental conduct” – wrote on Facebook of the “brilliant insight” into Mr Lansman provided to her by her long-term partner Graham Bash, who is still a member of Jeremy Corbyn’s party in South Thanet, Kent.

In an analysis of Mr Lansman’s 30 year long political career, Mr Bash is quoted by Ms Walker as having said: “Until Jeremy became leader the issue of Israel and Zionism did not come up in my presence. But within the last few years his ‘Jewish exceptionalism’ has become apparent to me.”

Later Mr Bash, who is an outspoken Jewish anti-Zionist and a friend of Mr Corbyn’s,  suggests that Mr Lansman’s “absence of any Marxist perspective also meant that he was unable to resist nationalist/exceptionalist pressures (ideas that see Jews as exceptional).”

He adds: “I can understand this. Even though I was brought up in a left wing Jewish family I was still many ways – psychologically – a Jewish exceptionalist. And only years of Marxist training enabled me to overcome this.”

According to Ms Walker’s account, Mr Bash said Mr Lansman did not “have access” to this re-education of his views.

“And so it was the politics of soft Zionism began to affect him,” said Mr Bash. “He succumbed to it, and encouraged it and became part of the problem.”

It is understood that Ms Walker’s Facebook post is already the subject of one formal complaint to the Labour Party, with one complaint suggesting that the reference to “Jewish exceptionalism” “is redolent of the antisemitic theories of Gilad Atzmon.”

Mr Bash is on the JVL executive where he is listed as the group’s Political Officer. He is also an executive member of the hard-left Labour Representation Committee of which shadow chancellor John McDonnell remains president.

He has also edited the Labour Briefing newspaper, on whose editorial board Mr Corbyn once sat.

In recent years Mr Bash has led the attack on Mr Lansman’s leadership of Momentum, accusing it of “political degeneration.” He also opposed the expulsion from Labour of numerous activists accused of antisemitism, including his partner Ms Walker, who posted during a Facebook discussion that Jews were “chief financiers of the sugar and slave trade” and argued that “the Jewish Holocaust does not allow Zionists to do what they want”.

The JC has contacted Mr Lansman over the remarks by Mr Bash as reported by Ms Walker, but he did not wish to comment on something that may be put before Labour’s disciplinary body the NEC.

Mr Bash failed to respond to our request for comment. It is understood that Labour has launched an investigation into his conduct.