Labour's candidate in Thursday's Peterborough by-election signed a letter sent that said people had to be able to “speak freely” about Israel's “system of apartheid and ongoing ethnic cleansing” in the same way “Jewish members must be able to speak freely about the Holocaust.”
The letter – which opposed the adoption of the full IHRA code of antisemitism including examples of how criticising Israel could be antisemitic – was also signed by Elleane Green, who is suspended by Labour over her running of the Palestine Live Facebook group.
Also among the signatories were Lesley Anne Perrin, who resigned from Torbay Labour Party over posting Holocaust denial material online, Asa Winstanley, who called the Jewish Labour Movement an "Israeli embassy proxy" and members of the Labour Against The Witch-hunt group.
The revelation comes as Jewish Labour Movement (JLM) vowed not to campaign for Lisa Forbes, who had already been forced to apologise on Sunday for liking a Facebook post that said Theresa May had a “Zionist Slave Masters agenda”.
She also approved of a message claiming Islamic extremists were created by the CIA and Mossad.
Last August, her name was put to an open letter to Labour’s governing body, signed by more than 100 left-wing anti-Zionist campaigners, which was circulated by the pro-Corbyn fringe group Jewish Voice For Labour.
The letter appeared to call for the dismantling of the state of Israel, which is suggested was not “democratic” but an “apartheid state” and suggested instead a one state solution “in the form of a democratic state that grants equal rights to everyone lawfully residing within its borders.”
Ms Forbes backed the claim that: "Claiming that the State of Israel is a racist endeavour is not the same as denying Jewish people the right to self-determination.
"It is denying such self-determination at the cost of the ethnic cleansing of Palestinian people. It is denying self-determination in the form of an ethno-nationalist state.”
The letter added: "Our Palestinian members must be able to speak freely about the Nakba and about the current system of apartheid and ongoing ethnic cleansing just like our Jewish members must be able to speak freely about the Holocaust.”
It also expressed support for the Boycott Divestment, Sanctions movement, saying: “To endorse the BDS movement or to suggest that the State of Israel in its historic and current form is a racist endeavour are not expressions of antisemitism.”
On Tuesday, JLM singled out her support for the open letter as part of the reason it would not be campaigning for her.
It said: "To do so would be inconsistent with the views of our members, who have understandably and clearly called for a culture of zero tolerance towards antisemitism in the Labour Party.
"We had warned the the party that they needed to be much more thorough in checking membership and vetting candidates," JLM said.
"We've told them that their refrain of zero tolerance stance on racism needs to be translated into action. We've been ignored."
The statement continued: "We're angry and disappointed but not surprising. Until the party faces up to the depth of the problem and starts taking real action, this will continue to happen."
On Sunday in a joint statement, the Board of Deputies of British Jews, the Jewish Leadership Council and the Community Security Trust said the revelations around Ms Forbe’s Facebook conduct “brings in to question her suitability for public office”, adding her claim to have not seen the words “stretches the limits of credulity”.
The JC contacted Labour for comment over her support the anti-IHRA letter.