LONDON (Reuters) - British Jewish groups held a street protest outside parliament on Monday against opposition Labour Party leader Jeremy Corbyn, accusing him of failing to tackle anti-Semitism in party ranks because of a far-left world view hostile to Jews.

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Since unexpectedly becoming Labour leader in 2015 after decades spent on the left-wing fringes of the party, Corbyn has repeatedly faced accusations of turning a blind eye to anti-Semitic comments in the party and among groups he supports.

“He is repeatedly found alongside people with blatantly anti-Semitic views, but claims never to hear or read them. Again and again, Jeremy Corbyn has sided with anti-Semites rather than Jews,” the Board of Deputies of British Jews and the Jewish Leadership Council said in an open letter late on Sunday.

Around a couple of thousand protesters packed out the green opposite parliament, carrying signs and singing, according to a Reuters photographer at the event.

One of the placards read “For the many, not the Jew” - a play on Labour’s “For the many, not the few” campaign slogan.

Corbyn responded on Monday with an open letter to both groups in which he recognized that anti-Semitism had surfaced within his party, apologized for the pain this had caused, and pledged to redouble his efforts to stamp it out. He offered to meet both groups’ leaders urgently to discuss their concerns.

The issue had flared up again last week after it came to light that in 2012 Corbyn questioned a decision by London local authorities to remove a street mural depicting men in suits with big noses playing Monopoly on the backs of naked people.

“The idea of Jewish bankers and capitalists exploiting the workers of the world is an old anti-Semitic conspiracy theory,” Corbyn wrote in his open letter on Monday. “I am sorry for not having studied the content of the mural more closely before wrongly questioning its removal in 2012.”

Several Labour members of parliament said they would join the protest on Monday, exposing internal divisions within Labour that had been papered over after Corbyn led the party to a stronger-than-expected showing in a general election last June.

“While Jeremy is not himself anti-Semitic, he has allowed himself to become the poster boy of anti-Semites everywhere,” said veteran Labour lawmaker Margaret Hodge, the daughter of Jewish refugees from Germany and Austria, in a statement.

In their open letter, the Jewish groups denounced what they described as the far left’s “obsessive hatred of Zionism, Zionists and Israel” and gave examples of how that often translated into overtly anti-Semitic language. They said Corbyn’s “empty statements” condemning anti-Semitism had got nowhere near dealing with the problem.

In his response, Corbyn, a vocal supporter of Palestinian rights and critic of Israel for several decades, acknowledged that anti-Semitism had sometimes been woven into criticism of Israel.

“Comparing Israel or the actions of Israeli governments to the Nazis, attributing criticisms of Israel to Jewish characteristics or to Jewish people in general and using abusive phraseology about supporters of Israel such as ‘Zio’ all constitute aspects of contemporary anti-Semitism,” he wrote.