Britain’s most senior Jewish religious leader stepped into the middle of the country's general election campaign Monday, warning that the “the very soul of our nation is at stake" and claiming that opposition Labour Party leader Jeremy Corbyn's handling of anti-Semitism allegations makes him “unfit for high office.”

Chief Rabbi Ephraim Mirvis, the spiritual leader of the United Kingdom’s Orthodox Jews, said Corbyn had allowed the “poison” of anti-Semitism to take root in his party.

Mirvis, writing in The Times of London, said Corbyn and his allies had failed to stop anti-Jewish prejudice within the party and “hounded” those who tried to challenge it.

Mirvis' op-ed represents a near-unprecedented intervention in the U.K.'s politics, which he described as “amongst the most painful moments” of his career.

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Corbyn has called anti-Semitism “a poison and an evil in our society” and said he is working to root it out of the party. Mirvis said that Corbyn’s claim to have dealt with all allegations of anti-Semitism is not true, adding that “the way in which the leadership has dealt with anti-Jewish racism is incompatible with the British values of which we are so proud.”

“Elections should be a celebration of democracy. However, just weeks before we go to the polls, the overwhelming majority of British Jews are gripped by anxiety," Mirvis wrote, later adding: "It is not my place to tell any person how they should vote. ... I simply pose the question: What will the result of this election say about the moral compass of our country?"

Labour’s election campaign has been dogged by repeated allegations that Corbyn — a longtime champion of the Palestinians — has allowed anti-Jewish prejudice to fester in the left-of-center party.

The governing Conservatives, meanwhile, are defending an election platform that is light on policy proposals, as they try to avoid squandering the party’s poll lead before the nation votes on December 12.

Prime Minister Boris Johnson’s party is focusing its campaign on a promise to “get Brexit done” by taking Britain out of the European Union on the currently scheduled date of Jan. 31.

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“When we get Brexit done, believe me we will unleash a tide of investment into this country,” Johnson told supporters as he campaigned Monday in north Wales.

Culture Secretary Nicky Morgan weighed in, acknowledging that leaving the bloc would only be “the first big step” to completing Brexit since it would be followed by negotiations on a new trade relationship with the bloc.

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In the upcoming election, which is taking place more than two years early, all 650 seats in the House of Commons are up for grabs. Johnson sought the early vote in hopes of winning a majority and breaking Britain's deadlock over Brexit.

The Associated Press contributed to this report.