The Labour Party has an anti-Semitism problem. This much has been obvious for years. The party’s repeated failure to address it made the current crisis inevitable.

It was in November 2015, a few months after his election as Labour leader, that Jeremy Corbyn was first reported by the Jewish Chronicle to have defended a flagrantly anti-Semitic mural in east London. But only when one of his MPs, Luciana Berger, raised the issue in late March 2018, did Mr Corbyn respond. His explanation – that he “did not look more closely at the image” – and his initial refusal to apologise was inadequate for an aspirant prime minister.

The Labour leadership’s handling of this scourge has consistently fallen short. In 2016, the party’s anti-Semitism inquiry (which followed the suspension of Labour MP Naz Shah and former London mayor Ken Livingstone) was undermined irretrievably when Mr Corbyn elevated Shami Chakrabarti, the “independent” author of the report, to the House of Lords. She was then appointed shadow attorney general.

It took a public demonstration led by the Board of Deputies of British Jews and the Jewish Leadership Council – a shameful moment in Labour’s 118-year history – for Mr Corbyn to issue a full apology. On 25 March, he rightly stated that left-wing criticism of Israel and of capitalism as a “conspiracy” (what the German social democrat August Bebel called the “socialism of fools”) too often degenerates into anti-Semitism. Indeed, more than 300 alleged cases have been referred to Labour since 2015 (74 of which are still pending). Yet 30 per cent of Labour Party members, according to a recent YouGov poll, believe that anti-Semitism is “not a serious problem” and is being “hyped up to undermine Labour” and the Corbyn leadership. Another 47 per cent acknowledge there is a problem but believe it is being exaggerated.

Until Mr Corbyn acknowledged the scale of the problem, there was no prospect of its resolution. But Labour’s challenge has only become clearer in the days since. Momentum director Christine Shawcroft was forced to resign from the party’s ruling National Executive Committee after arguing for the readmission of a man who posted an article denying the Holocaust. (She claims she did not see the post before commenting.) That was the correct decision, but it should have come more swiftly. The Labour leader should further support the expulsion of Mr Livingstone, who remains formally “suspended” by the party.

Mr Corbyn needlessly undermined his standing when on 2 April he attended a dinner hosted by the anti-Zionist group Jewdas. By prioritising an organisation which dismissed the anti-Semitism scandal as “a bout of faux-outrage”, the Labour leader risked appearing indifferent to the concerns of other Jewish groups.

Too often, Mr Corbyn has proved reluctant to leave his political comfort zone. As leader of the opposition, rather than merely a backbench MP, his duty is to build alliances and to engage in good faith with those he disagrees with. In the case of the Jewish community, Mr Corbyn has failed to do so.

Racism is not confined to Labour. In 2016, the Conservatives ran a shamelessly Islamophobic campaign against the then London mayoral candidate Sadiq Khan. Across Europe, anti-Semitism is proliferating on the far right as well as the far left (most virulently in Viktor Orbán’s Hungary). But before Labour can credibly confront the prejudice of others, it must purge itself of bigots, racists and fools.