By GREGORY KATZ and PAN PYLAS

LONDON (AP) — Labour Party leader Jeremy Corbyn struggled Tuesday to defuse harsh criticism about anti-Semitism leveled at both himself and the party by Britain’s chief rabbi.

In what was arguably his most difficult day in the general election campaign so far, Corbyn faced a multitude of questions over Chief Rabbi Ephraim Mirvis’ damaging remarks in The Times newspaper.

The influential rabbi implied that Corbyn was unfit for high office and that Labour’s efforts to tackle anti-Semitism were a “mendacious fiction.” The “overwhelming majority” of Britain’s Jews, he added, were “gripped by anxiety” about Corbyn’s possible election.

“A new poison, sanctioned from the top, has taken root in the Labour Party,” he said.

While voicing his disapproval of all forms of racism, including anti-Semitism, Corbyn declined repeatedly to apologize during a prime-time BBC interview for any anti-Semitism that has occurred in the Labour Party over the past few years.

“We will not allow anti-Semitism in any form in our society because it is poisonous and divisive, just as much as Islamophobia or far-right racism is,” Corbyn said in the interview with the veteran BBC broadcaster Andrew Neil.

Corbyn insisted he had “strengthened” Labour’s processes on how to deal with anti-Semitism in the party since a written warning was given to a member who questioned the number of people who died in the Holocaust.

“There are a very, very small number of people in the Labour Party that have been sanctioned as a result of complaints about their anti-Semitic behavior,” Corbyn said. “As far as I’m concerned one is one too many and I’ve ensured action (has been) taken on that.”

The ongoing questions about anti-Semitism have damaged traditionally strong ties between Britain’s Jews and the Labour Party, prompting many members to quit the party in disgust. Anti-Semitism is cited as one of the main reasons by many people as to why they won’t vote for Labour in the Dec. 12 general election.

The rabbi’s broadside represented a break from his traditional position of not commenting on party politics. Though Corbyn has been repeatedly criticized for tolerating anti-Jewish comments from party members, he’s not faced anything quite so acute from someone in the Jewish community’s hierarchy.

At a campaign event earlier, Corbyn sought to allay concerns by insisting that if he becomes prime minister, he wants to lead a government that has an “open door” to all faith leaders.

He said he would invite Mirvis and other religious leaders “to come talk to us about what their concerns are” and said no community would feel at risk because of their faith.

Corbyn, 70, has long been a champion of Palestinian rights and critical of the Israeli government. He has at times appeared to be sympathetic to the grievances of groups such as Hamas and Hezbollah.

The rabbi’s damaging column was published on the day Labour was launching its “race and faith” platform as part of its campaign to win voters with its views on tolerance and equality.

The left-wing party pledged in its platform to teach children about the legacy of the British empire, including slavery and colonialism, and also says it will treat attacks on places of worship as a specific aggravated offense.

Outside the launch event, protesters put up anti-Labour posters including one that read, “a vote for Labour is a vote for racism.”

Mirvis’ was not echoed by the whole Jewish community.

Alf Dubs, a Labour member of the House of Lords who came to Britain in the 1930s as a child refugee fleeing the Nazi, said he believed the attack had been “unjustified and unfair”.

Others from across the religious spectrum backed Mirvis.

Louise Ellman, a former Labour legislator who quit the party over the issue, said the chief rabbi’s column reflects “widespread concern and anxiety” across the mainstream Jewish community.

“The reason I have left the Labour Party is because I cannot ask people to vote for Jeremy Corbyn as prime minister while we have a Labour Party that is institutionally anti-Semitic,” she told the BBC.

The situation, she added, was “unprecedented.”

Archbishop of Canterbury Justin Welby said in a tweet that the chief rabbi’s comments should make clear to the country that many British Jews feel uneasy.

The Muslim Council of Britain praised the rabbi for speaking out and said it agreed with his conclusion that too many politicians have been silent while racism has spread.

The council said Muslims face hostility, particularly within the governing party led by Prime Minister Boris Johnson.

“This is an issue that is particularly acute in the Conservative Party, who have approached Islamophobia with denial, dismissal and deceit,” the group said.

All 650 seats in the House of Commons will be decided in the election, which was called by Johnson with the goal of getting a new Parliament that would back his Brexit policy.