British Jewish leaders blasted opposition Labour leader Jeremy Corbyn in an extraordinary public letter released on Monday, accusing him of backing anti-Semites “again and again.”

The Board of Deputies of British Jews and the Jewish Leadership Council said the veteran left-winger was “repeatedly found alongside people with blatantly anti-Semitic views” but “claims never to hear or read them.”

The letter accuses Mr. Corbyn of being unable to “seriously contemplate anti-Semitism, because he is so ideologically fixed within a far left worldview that is instinctively hostile to mainstream Jewish communities”.

The missive claimed there was a “repeated institutional failure” within Labour to tackle anti-Semitism and there was “literally not a single day” in which Labour spaces, either online or in meetings, did not repeat “slanders against Jews”.

A protest will be held outside the Houses of Parliament on Monday evening to reinforce the letter, which will see a number of Labour MPs – including Liz Kendall, John Woodcock, Michael Dugher and Ian Austin – join members of the Jewish community.

#EnoughIsEnough We call on members of our community and all those who oppose antisemitism to join us in Parliament Square at 5:30pm to show solidarity. https://t.co/S2nHp2a971 pic.twitter.com/lApuawcNrw — The JLC (@JLC_uk) March 25, 2018

In a statement released on Sunday evening, Mr. Corbyn declined to take any personal responsibility for the accusations. Instead he said:

I want to be clear that I will not tolerate any form of anti-Semitism that exists in and around our movement. We must stamp this out from our party and movement. We recognise that anti-Semitism has occurred in pockets within the Labour Party, causing pain and hurt to our Jewish community in the Labour Party and the rest of the country. I am sincerely sorry for the pain which has been caused.

The march and the letter come as Mr. Corbyn faces a challenge to debate anti-Semitism allegations in Parliament and “explain why you defend the world’s oldest hatred.”

The call has been made by Sajid Javid, Secretary of State for Communities and Local Government, who took to social media to say “enough is enough Jeremy Corbyn”, as pressure mounts for the opposition leader to explain why he questioned the removal of an anti-Semitic mural depicting a group of men huddled around a Monopoly-style board.

All this follows in the wake of polling which shows that British Jews have been abandoning the Labour Party since the election of Mr. Corbyn, and a recent survey revealed that four in five believe that Labour harbours anti-Semites in its ranks.