Jewish Labour members will boycott talks on tackling antisemitism after accusing party leaders of trying to deliberately “antagonise tensions” in the row over the issue, The Independent has learned.

The Jewish Labour Movement (JLM) said it was pulling out of discussions with the party’s working group on antisemitism because its faith that the Labour leadership wants to solve the crisis engulfing the party “has all but disappeared”.

It accused Jeremy Corbyn’s team of a “deliberately misleading approach” and “further inflaming tensions rather than tempering them”.

In an explosive letter seen by The Independent, JLM chair Ivor Caplin said the group “cannot participate in good faith” in further discussions until the party takes steps to prove it is serious about tackling antisemitism.

Instead, Labour has adopted ”a strategy that will only antagonise tensions further”, he said.

JLM’s withdrawal from the crunch talks will come as a blow to Mr Corbyn and Jennie Formby, Labour’s general secretary, as they attempt to gain control of the row gripping the party. It is understood that no other formal talks are ongoing between JLM and the Labour leadership.

It came as Mr Corbyn faced questions over a memorial event he attended in Tunisia in 2014, at which a commemoration was held for the terrorists behind the Munich Olympics massacre that left 11 Israeli athletes dead. The Labour leader admitted being “present” at the ceremony but denied having laid a wreath at the attackers’ graves.

Labour’s working group on antisemitism was set up by the party’s ruling executive in a bid to regain control of the issue and work with the Jewish community to resolve a series of bitter disputes.

It consists of senior members of the national executive committee (NEC), including shadow cabinet ministers, leading trade unionists and the chair of the influential Momentum group, Jon Lansman.

The second meeting of the group was due to take place on Wednesday, but Mr Caplin said JLM would be rejecting an invitation to take part in the talks.

In a letter to Ms Formby, copied to all members of the NEC, he said: “You will be aware that we have raised a number of concerns directly with you, your office and with the leader’s office over a significant period of time.

“Specifically, we raised very clearly our frustrations and concerns that the antisemitism working group had been convened by the NEC without our engagement. Had the party sought to address matters of concern from any other affiliated organisation, they would have done so with their full involvement. This has not been the case.”

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Mr Caplin said JLM had asked to have a permanent representative on the antisemitism working group, but that this had been rejected.

Instead, the organisation was invited to a meeting but later had its invitation withdrawn, with JLM representatives forced to wait outside while NEC members discussed whether they should be let in.

He wrote: “After invitations were offered explicitly inviting JLM, these invitations were subsequently withdrawn. As NEC members spent the initial moments of the meeting in question confirming they had no objection to JLM’s presence, our representatives were left waiting in the reception of your building.”

JLM was reportedly told that only members of the ruling executive were allowed to take part in the working group, but Mr Caplin said this claim was “completely undermined” by the inclusion of Baroness Chakrabarti, the shadow attorney general and author of a report of antisemitism in Labour, who is not a member of the NEC.

He wrote: “Instead, the party has now embarked on a strategy that will only antagonise tensions further. Despite our numerous warnings, we can only conclude that this has been done so with intent.

“Unless and until we are able to obtain satisfactory outcomes to the below, the Jewish Labour Movement cannot participate in good faith with the antisemitism working group’s activities.”

And he added: “We remain of the view that the party must act without delay to ease the considerable tension that has grown over the last few months. At all points during this crisis, JLM has offered constructive advice and suggestions to overcome the challenge we now find ourselves in. Faith that the party wishes to reciprocate in the same manner has all but disappeared.”

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Mr Caplin laid out four criteria that Labour must meet in order for JLM to re-enter discussions. They are: adopting in full an internationally recognised definition of antisemitism, responding to formal complaints about NEC member Peter Willsman and Labour MP Chris Williamson, and ending a disciplinary investigation into MP Ian Austin.

The issue of the International Holocaust Remembrance Alliance (IHRA) definition has been at the heart of Labour’s antisemitism crisis in recent weeks. The NEC’s decision not to adopt four of the IHRA’s 11 examples of antisemitic behaviour in the party’s new code of conduct was widely condemned by Jewish community leaders and Labour MPs.

Mr Corbyn is under mounting pressure to back down on the matter and has suggested he is ready to accept at least three of the four examples originally omitted. But despite trade union leaders having joined calls for the full definition to be adopted, the Labour leadership is set to maintain its opposition to the other example, which says it is antisemitic to suggest the creation of a state of Israel is a “racist endeavour”.

Labour had promised further consultation with Jewish groups, including JLM, on the issue but it is unclear whether this will now take place.

Mr Caplin wrote: “No code of conduct on antisemitism developed in isolation without the involvement of JLM or the wider Jewish community will maintain any confidence. This belligerent position on behalf of the party is also at odds with its own decision in December 2016 to adopt the full IHRA definition alongside the working examples.

“The subsequent decision by the party to revisit the IHRA document and amend its contextual examples without consultation represents a backward step in the party’s handling of antisemitism.

“The briefing by the party and the leader’s press office to the media that only one contextualised example remains in discussion is further evidence of the deliberately misleading approach being taken, further inflaming tensions rather than tempering them.”

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Mr Caplin also said JLM had received no response to formal complaints it had made about Mr Willsman and Mr Williamson, and would not consider re-entering talks until it did.

Mr Willsman was recorded at a recent NEC meeting claiming the antisemitism row was the fault of Jewish “Trump fanatics”, but party officials declined to take disciplinary action against him, saying his apology was the end of the matter.

JLM also made a formal complaint about Mr Williamson after accusing him of “repeatedly sharing platforms with expelled and suspended members of the Labour Party” and “regularly denying that antisemitism exists within Labour”.

In his letter to Ms Formby, Mr Caplin said of the MP: “His behaviour continues to undo any small progress achieved in dealing with this crisis.”

JLM also demanded the party drop disciplinary proceedings against MP Ian Austin, who is being investigated after a confrontation with party chairman Ian Lavery over the antisemitism crisis.

A similar investigation into another MP, Dame Margaret Hodge, was dropped last week.

Mr Caplin said there was “considerable anger and frustration at how the party has managed to recklessly and deliberately exacerbate tensions between it and the Jewish community”, adding: “Pursuing Ian Austin MP can serve no useful purpose.”

He also said JLM was “incredibly disappointed” that NEC members are due to be given antisemitism training provided by an unknown organisation, rather than JLM. This was further evidence Labour attempts “to deliberately undermine its formal Jewish affiliate and add to further tension”, he said.

A Labour source said: "The party has always sought to work constructively with JLM and invited them to join the working group meeting.