Jeremy Corbyn ally Len McCluskey, the general secretary of Unite the Union, has accused leaders of the Jewish community of “intransigent hostility”, saying their allegations of antisemitism in the Labour Party are "wildly exaggerated".

He wrote he was "at a loss to understand the motives" of Board of Deputies, the Jewish Leadership Council and the Jewish Labour Movement, saying they should "abandon their truculent hostility".

In a blog for HuffPost UK, he also accused the JC and two other Jewish newspapers, which wrote a joint editorial claiming Mr Corbyn poses an "existential threat" to Jewish life, of “a thoroughly irresponsible act of fear-mongering”.

He wrote: “I am at a loss to understand the motives of the leadership of the Jewish community – the Board of Deputies, the Jewish Leadership Council and the Jewish Labour Movement.

“They raised entirely proper concerns, but have simply refused to take ‘yes’ for an answer.”

“What is the response from the leading Jewish community organisations to this record of reaching out, of understanding, and of action?

"Intransigent hostility and an utter refusal to engage in dialogue about building on what has been done and resolving outstanding difficulties."

 “I therefore appeal to the leadership of the Jewish community to abandon their truculent hostility, engage in dialogue and dial down the rhetoric, before the political estrangement between them and the Labour Party becomes entrenched.”

The union boss said the leadership of the Jewish community should “grasp the hand stretched out towards them”.

But Mr McCluskey, a close ally of the Labour leader, also called for the party to adopt the International Holocaust Remembrance Alliance (IHRA) definition of antisemitism.

A Board spokesperson said: “We note that Len McCluskey has advocated the adoption of the full IHRA definition of antisemitism and its illustrative examples.

"However, his attack on the Jewish community is both unfair and unwarranted. We have had a deluge of words from the Labour leadership.

"It is about time that the Party resolved this crisis by taking the firm and decisive action which the communal leadership set out for them in detail months ago. They have so far failed to do what is right.”

The party has been mired in a standoff with the Jewish community after it rejected the definition in favour of its own, which omits examples of how criticising Israel can be antisemitic.

This week the leaders of two other unions, Unison and GMB, also publicly called for the adoption of the code in full.