Few can doubt the pleasure with which, if he is elected his party's leader this weekend, Jeremy Corbyn will drive the final nails into the coffin of New Labour.

Throughout the leadership campaign, Corbyn has sought, with ill-disguised glee, to resurrect those Old Labour sacred cows which Neil Kinnock, John Smith and Tony Blair slaughtered as they dragged the party back to electability. But there is one element of its history that Corbyn seems less concerned to revive: the once-close bond between the party and the Jewish community.

That relationship was never warmer than in the summer of 1945. Bolstering the ranks of the formidable parliamentary majority which swept Clement Attlee into Downing Street in July 1945 were 26 Jewish Labour MPs. Among their number were some - like Harold Lever, Manny Shinwell and Ian Mikardo - who would become leading figures in the party and household names.

Although the precise breakdown of how Britain's Jews voted in 1945 is unknown, Labour captured the vast majority of seats in which they were most heavily concentrated. In part, the result reflected the desire of working-class Jews, like their fellow countrymen, to punish the Conservatives for the Depression and mass unemployment of the 1930s and elect a Labour government committed to the introduction of a ''cradle-to-grave'' welfare state.

But Labour's appeal to many Jews also stemmed from their distaste for the Tory party. Memories of the Aliens Act of 1905; the blatant discrimination displayed by the Conservatives' allies on the London County Council; appeasement; and the 1939 White Paper, which reneged on the Balfour Declaration and sought to curtail Jewish immigration to Palestine, died hard. Moreover, what Stuart Bell in his history of the party terms "an undercurrent of antisemitism in Conservative circles" led many Jews to distrust the Tories. That there was only one Jewish Conservative - Daniel Lipson, who sat as an independent thanks to the antisemitism of Cheltenham Tories who refused to adopt him as their candidate in 1937 - in the Commons for a decade after 1945 seemed to underline the point.

In contrast to the Tories, Labour's commitment to the Zionist cause appeared unimpeachable. It had opposed the White Paper and in 1944 reiterated its support for a Jewish homeland which it deemed "irresistible" after the "unspeakable atrocities" perpetrated by the Nazis. But in November 1945 Ernest Bevin announced that the new government intended to maintain the restriction on Jewish immigration into Palestine its predecessor had imposed six years previously. This betrayal would try the loyalty of many Jewish Labour supporters.

A decade later, the party would test that loyalty again when, during the height of the Suez crisis in 1956, Hugh Gaitskell likened Israel to a thief, suggesting that Anthony Eden resembled a policeman whose policy has been "to go in and help the burglar shoot the householder". Such language compounded the betrayal of 1945, allowing Tories like Sir Keith Joseph, fighting a by-election in Leeds North East six months previously, to brand Labour "the party of Bevin, which left Israel without protection".

In reality, though, Labour's support among Jews was neither as solid nor unassailable as it had appeared in 1945. Throughout the interwar years a tradition of Jewish Toryism stretching back to the late Victorian era remained alive. As upwardly mobile second-generation immigrants escaped the East End for the suburbs - a trend already evident in the 1930s but which accelerated after the war - their attachment to Labour began to wane. "To the Toryism of the established Jewish gentry was thus added the Toryism of the Jewish noveaux riches," writes Geoffrey Alderman in The Jewish Community in British Politics. Even in 1945 seats with sizeable Jewish communities, like Finchley, Hendon South, Leeds North, and Middleton and Prestwich, were retained by the Tories.

But as Margaret Thatcher found when she was selected to fight Finchley for the Tories in 1958, the nascent growth of Jewish suburban Conservatism was not irreversible. "The Jewish faith have allied themselves to Liberalism," she warned Conservative Central Office soon after the Tories had chosen her. The implication of several Tory councillors in the exclusion of Jews from the Finchley Golf Club served as a potent reminder of the casual antisemitism which still infected the party's grassroots. Over the next three decades, Thatcher never forgot that lesson.

When Labour returned to government in 1964 it was led by Harold Wilson, a man who, writes his biographer, Philip Ziegler, was determined to "expiate the sins of Bevin". Mikardo believed the prime minister had but one "doctrinal belief … his devotion to the cause of Israel". In the likes of Barbara Castle, Richard Crossman, George Brown and Ted Short, he found heavyweight Labour allies. When the Jewish state was imperilled in 1967 and 1973, Wilson was steadfast in his support. Indeed, following Ted Heath's imposition of an arms embargo during the Yom Kippur War, it was the Tories' support for Israel that came under question.

Labour didn't simply attract Jewish support because of Wilson's Zionism. As Stephen Brook recalls in his study of British Jewry: "Growing up in the 1960s it was natural to assume that anybody with brains and a conscience supported Labour … Jews were attracted to the more forward-looking Labour party, largely because of its enlightened views on social matters." Moreover, within the party Jews such as Leo Abse and Sydney Silverman were at the forefront of liberal reforms such as the decriminalisation of homosexuality and abolition of capital punishment.

Both Tony Blair and Gordon Brown followed very much in Wilson's tradition: their modernising politics, married to support for Israel, enabled them to win back centrist Jews who had fled into Thatcher's welcoming arms when Labour lurched to the left in the 1980s.

However, with its inflammatory rhetoric and Manichean view of the Israeli-Palestinian conflict, Labour's hard left has constantly threatened to drive a wedge between the party and its Jewish supporters, as Ken Livingstone's two spells in charge of London's government in the 1980s and 2000s demonstrated. Even for many Labour Jewish voters, Livingstone's behaviour - such as his declaration in 1984 that Jews "have been organising here in London, and throughout Britain, into paramilitary groups which resemble fascist organisations" or his seeming tolerance of antisemitic Islamic clerics 20 years later - were simply intolerable.

Unsurprisingly, Livingstone has been a vociferous supporter of Jeremy Corbyn, while his Socialist Action Trotskyite allies are prominent among the leadership hopeful's team. If Corbyn wins, Labour may have managed to elect as its leader one of the country's few politicians with even less appeal to the Jewish community than the former London mayor. That, alone, will be quite an achievement.