Britain’s former chief rabbi, Lord Jonathan Sacks, branded the Labour Party leader Jeremy Corbyn a dangerous anti-Semite in an interview published Tuesday.

In a devastating critique of the opposition leader, Sacks accused Corbyn of giving “support to racists, terrorists and dealers of hate, who want to kill Jews and remove Israel from the map.” The Labour leader, Sacks said, uses “the language of classic prewar European antisemitism.”

Corbyn has been under mounting attack for his own allegedly anti-Semitic positions and for failing to root anti-Semitism out of Labour, Britain’s main opposition party.

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The comments that sparked Sacks’s denunciation were made by Corbyn in a 2013 speech at the Palestinian Return Centre in London, where Corbyn said of a group of British “Zionists”: “They clearly have two problems. One is they don’t want to study history and, secondly, having lived in this country for a very long time, probably all their lives, they don’t understand English irony either.”

In an interview with the New Statesman magazine, Sacks, who served as chief rabbi from 1991 to 2013, called those remarks the most offensive to have been made by a senior British politician for 50 years.

“The recently disclosed remarks by Jeremy Corbyn are the most offensive statement made by a senior British politician since Enoch Powell’s 1968 ‘Rivers of Blood’ speech,” said Sacks. “It was divisive, hateful and like Powell’s speech it undermines the existence of an entire group of British citizens by depicting them as essentially alien.

“We can only judge Jeremy Corbyn by his words and his actions,” Sacks went on. “He has given support to racists, terrorists and dealers of hate who want to kill Jews and remove from Israel from the map.”

Interpreting Corbyn’s comment about “Zionists” as a thinly veiled reference to Jews, Sacks said: “When he implies that, however long they have lived here, Jews are not fully British, he is using the language of classic pre-war European anti-Semitism. When challenged with such facts, the evidence for which is before our eyes, first he denies, then he equivocates, then he obfuscates. This is low, dishonest and dangerous.”

Warned Sacks: “He has legitimized the public expression of hate, and where he leads, others will follow.

“Now, within living memory of the Holocaust, and while Jews are being murdered elsewhere in Europe for being Jews, we have an anti-Semite as the leader of the Labour Party and her majesty’s opposition. That is why Jews feel so threatened by Mr Corbyn and those who support him.”

“For more than three and a half centuries, the Jews of Britain have contributed to every aspect of national life,” Sacks noted. “We know our history better than Mr Corbyn, and we have learned that the hate that begins with Jews never ends with Jews. Mr Corbyn’s embrace of hate defiles our politics and demeans the country we love.”

Corbyn’s 2013 remarks, which resurfaced last week, have prompted a fresh wave of criticism of Corbyn, including from some Labour MPs. Corbyn last week claimed that he had used the word Zionist “in the accurate political sense and not as a euphemism for Jewish people.”

Sacks spoke days after a petition was launched by a British anti-Semitism advocacy group calling for Corbyn’s resignation.

The Campaign Against Antisemitism, founded in 2014, insisted “Jeremy Corbyn must go.” It urged Labour’s lawmakers to act, noting that “only 52 Labour MPs [are needed] to propose a challenger, or Labour MPs could propose a vote of no confidence, or set up their own political party. We call on the Parliamentary Labour Party to take action.”

The petition, which quickly gained thousands of signatures, was posted to the change.org website on Saturday, the same day a Labour Party anti-Semitism campaign group filed a formal complaint against Corbyn over his 2013 “Zionists” speech.

The CAA petition railed against “events from Jeremy Corbyn’s disturbing past” that “have trickled into the light.”

Back when “he could speak his mind without fear of scrutiny, [Corbyn] blamed Islamist terrorist attacks on Israel; defended an appalling antisemitic mural; honored a sheikh banned from the UK for saying that Jews drink non-Jews’ blood; said that a Hamas terrorist whose life’s work was the murder of Jews was his ‘brother’; held a repulsive event on Holocaust Memorial Day in which Jews were accused of being the successors to the Nazis; tried to have the word ‘Holocaust’ removed from the title of Holocaust Memorial Day; laid a wreath at a memorial for the Black September terrorists behind the Munich Massacre; and now we have heard that he made euphemistic comments to suggest that Jews are somehow un-British and foreign to the ways of our country,” it charged.

The petition garnered 5,581 signatures in its first 20 hours online.

It charged that Corbyn “over many years…sought to defend, honor, assist and promote antisemites and the context is that his actions have been consistent with those of an ideological antisemite. We had hoped that the Labour Party might at some point rise to the defense of British Jews by removing Jeremy Corbyn or by demanding his resignation, but the institutions of the once proudly anti-racist Labour Party are now corrupted and will not act.”

Earlier Saturday, Labour’s internal anti-Semitism advocacy group, Labour Against Anti-Semitism, said it had lodged a formal complaint with the party against Corbyn for “anti-Semitism and for bringing the party into disrepute.”

On Friday, The Times of London published an editorial calling Corbyn “straightforwardly antisemitic,” and concluding that his comments should “render him ineligible for membership, let alone leadership, of a democratic party and for public office.”

The 2013, a Hamas-endorsed conference featured several controversial speakers, including one who advocated boycotting Holocaust Memorial Day and another who blamed Israel for the 9/11 terror attacks in New York.

The resurfacing of Corbyn’s 2013 speech was met with backlash from a number of Labour MPs and Jewish figures, with the editor of the Jewish Chronicle saying, “It’s almost impossible to read this as anything other than a reference to Jews.”

But Corbyn defended his remarks, insisting that his mention of “Zionists” was not a euphemism for the Jewish people.

In a statement quoted by The Guardian on Friday, Corbyn said he had become “more careful with how I might use the term ‘Zionist’ because a once self-identifying political term has been increasingly hijacked by anti-Semites as code for Jews.”

The incident is the latest of a string of revelations detailing Corbyn’s antipathy for the Jewish state, and highlights the widening gap between the British left and the country’s Jewish community.

Claims of anti-Jewish prejudice within Labour have grown since Corbyn, a longtime critic of Israel, was elected leader in 2015. UK Jewish groups have accused him of failing to expel party members who openly express anti-Semitic views.

The dispute recently boiled over after the party last month proposed adopting a definition of anti-Semitism that differed from the one approved by the International Holocaust Remembrance Alliance, a move that was met with anger from Jewish groups and the country’s chief rabbi.

In recent months, photos and videos have emerged of Corbyn and other Labour officials making anti-Semitic and virulent anti-Israel comments.

Two weeks ago, footage surfaced of Corbyn accusing Israel of committing genocide against Palestinians during a 2014 rally, as a Hamas flag waved behind him. Corbyn called the terror group “friends” prior to his election as Labour leader two years ago, a statement he has since walked back.

One of the photos published recently showed Corbyn hosting a panel featuring a senior Hamas officials in 2012, including members convicted of murdering Israelis in terror attacks.

Earlier in August, the Daily Mail published photos of Corbyn in 2014 laying a wreath at the grave of the Palestinian terrorists who murdered 11 Israeli athletes in the 1972 Munich Olympics.

Corbyn initially claimed he attended the ceremony at the Cemetery of the Martyrs of Palestine in Tunisia to commemorate the 47 Palestinians killed during an Israeli bombing raid there in 1985. But images recovered from a Palestinian Embassy archive by the paper showed Corbyn holding a wreath in front of a plaque dedicated to members of Black September.

“A wreath was indeed laid by some of those who were at the conference to those that were killed in Paris in 1992,” Corbyn later admitted, adding that he while he was present at the ceremony, he did not “think I was actually involved in it.”

Last week, Times of Israel editor David Horovitz detailed Corbyn’s years of activism on behalf of a Labour movement that sought to “eradicate Zionism” and replace Israel with a secular Palestinian state, and branded Corbyn “an anti-Semite and a racist.” Horovitz wrote that Labour, if it wants to root out anti-Semitism, must expel Corbyn.

In his 2013 speech, Corbyn spoke about the importance of history and of how necessary it was for people to understand the origins of the conflict between Israelis and Palestinians.

He then praised a speech he had recently heard by Manuel Hassassian at a meeting in parliament in which the Palestinian ambassador to the UK gave an “incredibly powerful” account of the history of Palestine.

Corbyn then added: “This was dutifully recorded by the, thankfully silent, Zionists who were in the audience on that occasion, and then came up and berated him afterwards for what he had said.

“They clearly have two problems. One is that they don’t want to study history, and secondly, having lived in this country for a very long time, probably all their lives, don’t understand English irony either. Manuel does understand English irony, and uses it very effectively. So I think they needed two lessons, which we can perhaps help them with.”

In a statement released on Friday, Corbyn said he had “defended the Palestinian ambassador in the face of what I thought were deliberate misrepresentations by people for whom English was a first language, when it isn’t for the ambassador.”