Britain's most senior rabbi claims the UK's opposition leader Jeremy Corbyn is "unfit for high office" over his handling of anti-Semitism allegations.
Chief Rabbi Ephraim Mirvis claims "a new poison" has taken hold of the UK Labour Party, which was "sanctioned from the very top" and left British Jews justifiably "gripped by anxiety" before the December 12 election.
On Tuesday, he was supported by the Archbishop of Canterbury Justin Welby, who said intervention by Mr Mirvis "ought to alert us to the deep sense of insecurity and fear" felt by many British Jews.
It is an unusual step by both during the lead-up to an election. No other chief rabbi has taken sides in an election campaign.
The Labour Party launched its "race and faith" policies on Tuesday, setting out its means to improve social justice and human rights, and promote racial equality.
Mr Mirvis has described Mr Corbyn's claim to have dealt forcefully with all accusations of anti-Semitism as "mendacious fiction".
In a scathing comment piece in The Times, he said Mr Corbyn was responsible for a failure of leadership that was "incompatible with the British values of which we are so proud".
"How complicit in prejudice would a leader of Her Majesty's opposition have to be to be considered unfit for office?" Mr Mirvis asked.
He said it was not his place to tell anyone who to support but he advised "every person to vote with their conscience".
Mr Welby said: "The chief rabbi's statement provides all of us with the opportunity to ensure our words and actions properly reflect our commitments to mutual flourishing and inclusion, for the common good."
On Tuesday Mr Corbyn said that if he became prime minister, he wanted to lead a government with an “open door” to all faith leaders.
He said he would invite Mr 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.
Earlier Labour said its leader was a "lifelong campaigner against anti-Semitism" who had "made it absolutely clear it has no place in our party and society".
"A Labour government will guarantee the security of the Jewish community, defend and support the Jewish way of life, and combat rising anti-Semitism in our country and across Europe," the party said.
The row is the latest in a long-running series of allegations about widespread anti-Semitism among members since Mr Corbyn, a lifelong supporter of Palestinian causes, took over as leader in 2015.
MPs have since resigned from the party, accusing the veteran socialist of allowing the problem to flourish in its ranks and doing little or nothing to tackle it.
"It is heartbreaking to see a party so many of us joined to fight racism and which had such a proud record of fighting for equality reduced to this," tweeted former member Ian Austin, who left Labour in February.
"Corbyn and company should be so ashamed."
Last week, Mr Welby and his deputy, Archbishop of York John Sentamu, warned candidates to reject hate speech during the campaign.
Labour has been dogged by the anti-Semitism controversy, with nine MPs quitting in February over the leadership's handling of the issue.
A 2016 report by Shami Chakrabarti, the former head of civil rights group Liberty, concluded the party was "not overrun by anti-Semitism".
But some members have since said it is.
The Equality and Human Rights Commission has launched a formal inquiry into whether Labour "unlawfully discriminated against, harassed or victimised people because they are Jewish".
Mr Corbyn has repeatedly insisted he is not anti-Semitic and has pledged to "root out" the problem, which he recognises has "occurred in pockets" within the party.
But critics have criticised him for failing to deliver, claiming thousands of complaints of anti-Semitism were not addressed.
Meanwhile, incumbent Prime Minister Boris Johnson faced a blow on Tuesday after a former Conservative deputy prime minister called for voters to back another political party.
Conservative veteran Michael Heseltine accused Mr Johnson of pursuing an "utterly disastrous" Brexit policy that would make the UK poorer, and told the public to back the Liberal Democrats.
The Conservative Party has been embroiled in controversy over claims of Islamophobia.
On Tuesday, Finance Minister Sajid Javid announced the party would launch an inquiry into Islamophobia within its ranks, saying it took criticism from the Muslim community seriously.
Mr Javid said in Manchester that the Conservative Party would "never, ever, as a party, tolerate anyone among our ranks who has any kind of prejudice to any group of people, whether based on their race, or their religion, or their gender".
"Some members of the Muslim community and others are saying, and I understand this, 'Is there more that you can do, in your procedures as a party, to root out anti-Muslim hatred?'" he said.
"That's why we will have an inquiry into what more we can do."
