Revealed: John McDonnell signed Early Day Motion welcoming launch of extreme anti-Zionist group

In a statement, he said the issue had “shaken us to the core really.”

He added: “We’ve got to resolve it within the Labour party certainly. But also, the members of the Jewish community are really suffering out there.

“We’ve had a massive increase in attacks on the Jewish community, daubing of cemeteries, it’s appalling that Jewish schools have to have security guards as well.

“We’ve got to resolve the issue in our party and then get out there to assist the Jewish community, campaign against anti-Semitism within our society overall.”

But McDonnell’s support for the IJAN, which was founded by anti-Israel activist Sara Kershnar, sparked anger amongst British Jewish groups on Wednesday.

A Jewish Labour Movement spokesperson told the JC: “The Labour Party Leadership has made it very clear that there is one set of rules for Jews, and one set of rules for their comrades. 

“The only way forward is via the roadmap set by the Jewish community; adopt the IHRA definition of antisemitism in full including all the examples, suspend the whip from Chris Williamson, bring the cases of antisemitism we were promised would be done by end of July to a close and place Pete Willsman under investigation, removing him from this summer’s NEC elections.

“The leadership of our Party have pursued a deliberate and reckless approach to the events of the last few days and weeks, from which there will be very soon, no return”.

The group – whose supporters include retired professor Moshe Machover and anti-Zionist academic Ilan Pappe -  makes no secret of its view of Zionism as a racist movement and its opinion that Israel is an apartheid state.

The charter of the organization openly states they are an “international network of Jews who are uncompromisingly committed to struggles for human emancipation, of which the liberation of the Palestinian people and land is an indispensable part. Our commitment is to the dismantling of Israeli apartheid, the return of Palestinian refugees, and the ending of the Israeli colonization of historic Palestine."

Another mission statement on their website also reads: “Do you wish to dissociate yourself from the Israeli ethnic cleansing of Palestine and the destruction of history, culture and self-governance? Do you believe there is no peace without justice? Do you feel enraged and saddened that the holocaust against Jewish people is being used to perpetrate other atrocities?”

Other statements include the claim: “It (Israel) continues a long history of Zionist collusion with repressive and violent regimes, from Nazi Germany to the South African Apartheid regime to reactionary dictatorships across Latin America.”

It is also stated that: “The Israeli colonial project must be brought to an end.”

A Labour Party spokesperson said: “John was welcoming the creation of an organisation that represented an important strand of radical Jewish political campaigning.

“Of course he didn't and doesn't endorse all of the language and views expressed in their charter.”