The left-wing leader of the British Labour Party, Jeremy Corbyn, has been condemned as “a figurehead for anti-Semitism” by Jewish leaders after a steady drip of reports over the past weeks revealed that he was a member of three secret Facebook groups in which people shared anti-Jewish conspiracies and propaganda, including one post where Corbyn directly criticized the removal of anti-Semitic graffiti.

The British Jewish Leadership Council posted an open letter to the Labour leader on Monday saying “enough is enough”—and accusing him of doing nothing to combat anti-Semitism in his party—after it was revealed that he questioned the removal of an anti-Semitic mural in London that showed several offensive stereotypes of Jewish bankers playing a game of Monopoly on the backs of workers.

A tweet from a Jewish lawmaker in Corbyn’s own party, Member of Parliament Luciana Berger, revealed that he responded to the post in a Facebook group about the artwork being removed by saying: “Why? You are in good company. Rockerfeller destroyed Diego Viera’s mural because it includes a picture of Lenin.”

After his post was criticized over the weekend, Corbyn backtracked, insisting he didn't notice the anti-Semitic imagery at the time. "I sincerely regret that I did not look more closely at the image I was commenting on, the contents of which are deeply disturbing and anti-Semitic," he said. "I am opposed to the production of anti-Semitic material of any kind, and the defence of free speech cannot be used as a justification for the promotion of anti-Semitism in any form."

However, the old Facebook post is the latest in a string of reports which linked Corbyn to anti-Semitic Facebook groups. At the beginning of March he was revealed to have been in a group where terms such as "ZioNazi" were used and conspiracy theories about Jewish involvement in 9/11 were shared among members. U.K. politics blog Guido Fawkes has since revealed Corbyn's membership of two further groups where people shared offensive anti-Semitic content.

The trail of damning reports have provoked unprecedented criticism from Jewish leaders in the U.K. who have organized a protest outside of the British Houses of Parliament on Monday afternoon as Labour lawmakers hold their weekly group meeting inside—though Corbyn will reportedly not be attending this week’s event.

In a scathing open letter, the Jewish Leadership Council said: “[Corbyn] never sees or understands the anti-Semitism, whether it is from overseas terrorist groups or local Facebook groups. Now, he belatedly acknowledges a mural was anti-Semitic. Like so much else in this area, it is far too little, far too late, with no serious attempt to understand or tackle the damage to Jews and the Labour Party.”

The statement went on: “Hizbollah commits terrorist atrocities against Jews, but Corbyn calls them his friends and attends pro-Hizbollah rallies in London. Exactly the same goes for Hamas. Raed Salah says Jews kill Christian children to drink their blood. Corbyn opposes his extradition and invites him for tea at the House of Commons. These are not the only cases. He is repeatedly found alongside people with blatantly anti-Semitic views, but claims never to hear or read them.”

Corbyn has desperately attempted to stave off the growing criticism against him. In a statement Sunday, he apologized, saying he will “not tolerate any form of anti-Semitism that exists in and around our movement,” and he promised to “stamp out” anti-Semitism that 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.”

But rather than follow his lead in being apologetic over the incidents, many of Corbyn’s supporters have leapt to his defense. The hashtag #PredictTheNextCorbynSmear trended on Twitter on Sunday evening, with supporters ridiculing the media over the Labour leader’s supposed unfair treatment at the hands of newspapers and broadcasters who they believe have exaggerated his connections to anti-Semites.

A Jewish pro-Corbyn group, Jewish Voice for Labour, has also organized a counter-protest against the Jewish Leadership Council’s gathering outside Parliament on Monday afternoon. The group said it was “appalled” by the open letter that criticized Corbyn, and said: “They do not represent us or the great majority of Jews in the party who share Jeremy Corbyn’s vision for social justice and fairness.”

Corbyn has said he will meet Jewish leaders to discuss the issue of anti-Semitism in the Labour party, but Jonathan Goldstein, the chair of the Jewish Leadership Council, said he’d received no formal invitation as of Monday morning. Goldstein told BBC Radio that Corbyn’s apology for anti-Semitism in “pockets within the Labour party” did not go far enough.

“This is the first time in my life time that the Jewish community has felt the need to take to the streets to campaign against the leader of a major political party,” said Goldstein. “Rightly or wrongly, Jeremy Corbyn is now the figurehead for an anti-Semitic political culture based upon obsessive hatred of Israel, conspiracy theories, and fake news and that is doing great harm not just to the Labour party but to Britain in a wider sense.”