London (CNN) On the day Britain's opposition Labour Party wanted the nation to focus on its plans for the UK economy, its election campaign was blown off course with scathing criticisms of party leader Jeremy Corbyn from the Jewish community and a former senior party figure.

Less than 24 hours after Tom Watson said he would stand down as the party's deputy leader and a lawmaker at the forthcoming December 12 election, former Labour minister Ian Austin made an extraordinary call for party supporters to vote for main rivals the Conservative Party, saying Corbyn was unfit to be prime minister.

Austin's attack on the Labour leader came on the same day a damning front-page editorial in the UK-based newspaper the Jewish Chronicle called Corbyn a "racist" and urged non-Jewish Britons to think carefully before casting their vote in the election.

"If this man is chosen as our next prime minister, the message will be stark: that our dismay that he could ever be elevated to a prominent role in British politics, and our fears of where that will lead, are irrelevant," read the article, published today but dated November 8.

"We believe that the overwhelming majority of British people abhor racism. We ask only that, when you cast your vote, you act on that."

Austin, once an aide of former Prime Minister Gordon Brown, quit the Labour Party earlier this year citing the party's failure to tackle anti-semitism.

Writing in the regional newspaper the Express and Star, based in Wolverhampton, England, the lifelong Labour Party supporter said he must "do everything I can to stop Jeremy Corbyn from getting into power."

"It has really come to something when someone like me says traditional decent patriotic Labour voters should vote for Boris Johnson and the Conservative Party this time," Austin, now an independent lawmaker, wrote.

"The Labour Party has been poisoned by racism, extremism and intolerance under Jeremy Corbyn's leadership."

In a radio interview on the BBC Radio 4 Today program on Thursday, Austin said: "I'm not a Tory but I wouldn't say Boris Johnson is unfit to be our prime minister in the way I say that about Jeremy Corbyn."

'Racism must be called out'

The condemnation of Corbyn and his leadership could harm the party's hopes of ousting Johnson's Conservatives from power and casts a shadow on the second day of campaigning, when the party had promised £150 billion ($192 billion) for schools, hospitals and housing should it win the election.

The Jewish Chronicle posted a preview of its front page on Twitter on Thursday, saying it wanted to reach out to those who would not normally read the newspaper.

Here's our front page this week - addressed not to our usual readers but to our fellow British citizens pic.twitter.com/7K5qi8GhBJ — The Jewish Chronicle (@JewishChron) November 7, 2019

In its condemnation of Corbyn, the Chronicle -- which describes itself as the world's oldest and most influential Jewish newspaper -- said it was "important" and "urgent" that non-Jews put themselves "in the shoes of another person, or another group."

According to the newspaper, polling from October showed that 87% of British Jews considered Corbyn to be an anti-Semite.

"History has forced our community to be able to spot extremism as it emerges -- and Jeremy Corbyn's election as Labour leader in 2015 is one such example," the editorial read.

The article said that Corbyn had "throughout his career ... allied with and supported antisemites," and drew attention to his self-proclaimed "friendships" with representatives from Hamas and questionable associations with Holocaust deniers and anti-Zionists.

Since becoming Labour Party leader in 2015, Corbyn has been criticized as an outspoken critic of Israel and campaigner for Palestinian rights.

He was widely condemned for being present at a 2014 wreath-laying ceremony in Tunisia at the grave of the perpetrators of the 1972 Munich attack, in which 11 Israeli Olympians were killed by Palestinian militants.

Questions of whether the Labour Party contains strands of anti-Semitism have been on the rise in recent years and, at best, Corbyn has been accused of turning a blind eye to the resurgence of anti-Semitism within British politics and the party itself.

"There were some who hoped that he might change as leader. The opposite has happened," the article continued.

"The near total inaction of Mr Corbyn and the rest of the Labour leadership in dealing with antisemites in the party has both emboldened them and encouraged others.

"Indeed, Mr Corbyn and his allies have actively impeded action against the racists."

"Is it any wonder Jews worry about the prospect of Mr Corbyn as prime minister?" the paper asked.

Responding to the criticisms, a spokesperson for the Labour Party said Prime Minister Johnson could not be trusted.

"He has been sacked twice for lying, he conspired to have a journalist beaten up and he's trying to mislead the public about his plans for a sell-out Brexit that opens up our NHS to Donald Trump and could lead to £500 million a week going to big US drug companies. He is not fit to be prime minister," the spokesperson told CNN.

"Labour is running the most radical, people-focused campaign this country has ever seen because we need to transform our country after a decade of failure and cuts that have held our communities back."