Antisemitism is and must be morally repugnant to every person who believes in liberal and anti-racist values. Most members of the Labour party, and of most other parties too, are in no doubt about that. The opening line of the Chakrabarti report in 2016 – “the Labour party is not overrun by antisemitism” – was true at the time and remains true now. Jeremy Corbyn was accurate to talk this week of “pockets” of antisemitism within the party. But this does not deal with the issue. Not being overrun is not good enough. One pocket is one too many. It does not make the issue minor. Under Mr Corbyn, Labour has not been quick, clear or uncompromising enough to deal with those shameful remaining pockets.

This is not to make the mistake, too readily made by Mr Corbyn’s political enemies, of pretending that Labour is the only British political party or the only demographic in British society to be infected with antisemitism. It was a Conservative MP, not a Labour one, who complained in the House of Commons in 2014 about “well-funded powerful lobbying groups and the power of the Jewish lobby in America”. Those on the far right remain much more commonly antisemitic than those on the far left. But two (or more) wrongs don’t make a right. A 2017 study found that while only 2% of British people could be called “hard core” antisemites, about 30% hold one or two viewpoints that most Jews would consider antisemitic. No one can afford to be complacent about either figure.

Yet to acknowledge that antisemitism is more widespread than the Labour party and is not general within the Labour party is not to let Labour off the hook about its own responsibilities. Antisemitism is not merely morally wrong, though that’s serious enough, but politically dangerous. The mural in east London featuring anti-Semitic tropes that sparked the protests should, at any time, have been met with unqualified repudiation. Mr Corbyn must beware creating a liability for his party by not acting or by appearing not to act. Too often he gives the impression that on this issue he does not quite possess what the late leftwing historian EP Thompson once called “the nerve of outrage”. His latest statement on the issue is another that lacks such a jangling nerve.

To be “sincerely sorry for the pain which has been caused” is not the approach of a leader who, faced with such a vile force, should give a clear lead and ensure there is no hiding place for antisemitism. It’s not as if Mr Corbyn has proved incapable of decisive leadership on other issues. Nor is it as if he is insensitive to the fears of other ethnic or religious groups. He needs to bring the same decisiveness and the same sensitivity to Jewish complaints and fears – and he needs to do this now. If he does not engage, there is a danger that the argument about his response will become hardened and will entrench fear, hate and suspicion.

It would be wrong to suggest that every forum online – or offline – is contaminated. Yet that is not a reason to downplay the core complaints. That two Jewish community organisations – the Board of Deputies and the Jewish Leadership Council – have written in the strongest terms and taken to the streets is a sign not of obsession or partisanship but of fear and desperation. Nor should Mr Corbyn’s supporters dismiss the attacks because they may have been fanned by the Labour-hating press, or because they have created a social media frenzy. Hating Labour is what most newspapers do. Frenzies are what social media is about. If Mr Corbyn wants to stop the allegations, he should focus on eradicating the antisemitism.

This applies even more with the wider questions of the Middle East. This latest episode is not about Israel. It’s worth repeating that there is nothing anti-Jewish in criticising Israel’s conduct: Jews and Israelis do so every day. But it is antisemitic to dismiss every heartfelt complaint of anti-Jewish racism as an attempt to stifle discussion of Israel, for it suggests that Jews never act in earnest, but are rather motivated by an ulterior motive. Mr Corbyn, who cares passionately about the Middle East and racism, cannot elevate himself above this reality. But that is the mistake he is making, and it is diminishing both his moral and political authority.