LONDON — On the more polite BBC political affairs shows, what was once described as the British Labour Party’s “problem” with ­anti-Semitism has burst into an all-consuming “crisis,” engulfing opposition leader Jeremy Corbyn, who in recent days has been forced to apologize, not once but twice, and vow that anti-Jewish “poison” has no place in his movement.

Labour has spent the heat wave of midsummer twisting ­itself into knots over accusations that the party and its leader have repeatedly condoned anti-Semitism.

Critics charge that Labour cannot untangle some members’ fierce condemnation of Israel’s treatment of Palestinians from raw statements about the Jewish state’s right to exist.

Equally alarming to British Jews and others are the continuing revelations: that Corbyn hosted a 2010 panel where Israelis were compared to Nazis or that in 2012 he defended an artist’s freedom of speech but failed to condemn the London mural that depicted Jewish bankers playing monopoly on a board balanced on the bent backs of the workers.

There have been other eruptions in previous years, including over Corbyn’s paid appearances on Iranian state TV and his support for Hezbollah and Hamas, both sworn enemies of Israel, which Corbyn once called “friends.” (He has since said that was wrong.)

All this history is more important today, his critics say, because of the weakness of Prime Minister Theresa May and her Conservative government gives Corbyn and Labour a real shot at power.

Corbyn has strenuously denied any anti-Semitism on his part but concedes that relations between the Labour Party and British Jews are at a new low.

His defenders insist that while there are certainly a few anti-
Semitic voices among the 500,000 Labour Party members, it is a very small number, and no more than among the Conservatives.

Corbyn’s supporters go further, saying their opponents are hyping the issue to smear the party and its leader.

One close ally, Peter Willsman on Labour’s ruling body, claimed that “Trump fanatics” in Britain’s Jewish community were making unfounded claims of anti-
Semitism, according to tape recording obtained by the Jewish Chronicle newspaper.

Yet what makes the charge especially challenging for Corbyn is that the howls of criticism are not just coming from the outside — from traditional antagonists, from Tories and tabloids — but from leaders of the usually staid Jewish establishment and his fellow Labour Party members.

At the center of the current controversy is the party’s refusal to fully adopt widely accepted examples of anti-Semitism promulgated by the International Holocaust Remembrance Alliance. Labour has resisted the suggestion that it may be anti-
Semitic to compare contemporary Israeli policies to those of the Nazis or to claim that Israel’s very existence is a racist endeavor.

Corbyn, who has spent his career in Parliament as a staunch supporter of Palestinians, maintains that, as a matter of free speech, people should be able to condemn Israel without fear of being branded anti-Jewish. “In the 1970s some on the left mistakenly argued that ‘Zionism is racism.’ That was wrong, but to assert that ‘anti-Zionism is racism’ now is wrong too,” he wrote in the Guardian.

This position has stirred a strong reaction from Britain’s Jewish community. In an unusual step, the three leading Jewish community newspapers last month published a joint editorial on their front pages, warning of “an existential threat to Jewish life in this country that would be posed by a Jeremy Corbyn-led government.”

The editorial continued, “With the government in Brexit disarray, there is a clear and present danger that a man with a default blindness to the Jewish community’s fears, a man who has a problem seeing that hateful rhetoric aimed at Israel can easily step into antisemitism, could be our next prime minister.”

The broadside in the Jewish press was followed by a letter signed by 68 British rabbis, condemning the Labour leadership for choosing “to ignore those who understand antisemitism the best, the Jewish community.” 

Among the objectors within the party is longtime Labour parliamentarian Dame Margaret Hodge, who last month called Corbyn “an anti-Semite and a racist” to his face over his handling of the dispute. Labour leaders announced a disciplinary investigation of Hodge, with the threat of suspending her from the party (then quickly dropped the inquest).

This month, Labour deputy Tom Watson added to the pressure on Corbyn. “This is one of those moments when we have to take a long, hard look at ourselves, stand up for what is right and present the party as fit to lead the nation — or disappear into a vortex of eternal shame and embarrassment,” Watson said to the Observer newspaper

The deputy found himself facing a #ResignWatson social media campaign organized by Labour’s hard left. Labour official George McManus took aim at him for taking donations from a businessman prominent in Britain’s Jewish community. “Apparently Watson received £50,000+ from Jewish donors. At least Judas only got 30 pieces of silver,” McManus wrote in a Facebook post that earned him a suspension.

Corbyn has denied that he or his party represent an “existential threat” to Jewish life in Britain, dismissing that as “the kind of overheated rhetoric that can surface during emotional political debates.”

He said that Labour is the “natural home” for Britain’s 270,000 Jews.

“But I do acknowledge there is a real problem that Labour is working to overcome,” Corbyn wrote in the Guardian.

“Labour staff have seen examples of Holocaust denial, crude stereotypes of Jewish bankers, conspiracy theories blaming 9/11 on Israel, and even one individual who appeared to believe that Hitler had been misunderstood,” Corbyn revealed.

In a video address to Labour Party members, Corbyn said: “We have been too slow in processing disciplinary cases of, mostly, online anti-Semitic abuse by party members. We are acting to speed this process up.”

 In Britain, ordinary members who pay a few pounds to join — not just elected leaders — can be suspended or expelled from the parties. A Labour Party member, for instance, who in a recent podcast asserted that former prime minister Tony Blair was “unduly influenced by a cabal of Jewish advisers” was asked to attend a racism awareness course. He refused.

Speaking of the Labour leadership, Deborah Lipstadt, historian and author of “Denying the Holocaust,” told The Washington Post: “Whether they are anti-Semites or not is immaterial. They are indulging anti-Semitism, and they have been giving a very wide berth to people who engage in anti-Semitism.” 

She added: “When they look at Jews, they see power; they see control. They find it very hard to accept the Jew as a victim.”

Michael Segalov, a journalist and Labour activist, who is also Jewish, agreed that the party was slow to act against anti-Semitism, in part because years of unfounded attacks — that Corbyn was a Czech spy, for example — had left Labour with “a bunker mentality.” 

Segalov said that he’s seen a shift recently, that his party is now directly confronting the issue and that Corbyn should be credited with making clear statements. 

He pointed to the Labour leader’s warning this month that those “who dish out antisemitic poison” are “not my supporters and have no place in our movement.”

James McAuley in Paris contributed to this report.