It’s a reasonable expectation that our political leaders should set an example when it comes to bigotry and racism. But in recent months, a Labour party has emerged that has been far too slow to respond to antisemitism in its ranks. “The Labour party is not overrun by antisemitism,” began Shami Chakrabarti’s June 2016 inquiry into antisemitism in Labour. But what it entirely failed to acknowledge is that some traditions on the left have long had a problem with antisemitism, and that as they have grown in influence within the Labour party, antisemitism has reared its ugly head. Three hundred cases have been referred to the party’s disciplinary process since 2015. Not three, or 30, but 300.

As the home affairs committee 2016 inquiry into antisemitism pointed out, it has distinct characteristics: “Antisemitic abuse often paints the victim as a malign and controlling force rather than as an inferior object of derision.” The report also notes that “the majority of antisemitic abuse and crime has historically been, and continues to be, committed by individuals associated with (or motivated by) far rightwing parties and political activity”. But on the left, anti-capitalism has sometimes bled into antisemitism, and legitimate criticism of the Israeli government has given way to racist condemnation of Jewish people.

Antisemitism is, as noted above, not limited to the British left. But there are reasons why some parts of the self-defining anti-racist left have been vulnerable to antisemitism, and the Labour party will never succeed in ridding itself of this evil unless it is prepared to confront them head-on.

The Labour leadership has shown no signs it is willing to do this. There is no suggestion that Jeremy Corbyn personally holds antisemitic views, but he is rooted in left cliques where antisemitism has been a problem. This makes it even more important that he acknowledges those issues.

Instead, his standard response has been to condemn it, along with “all other forms of racism”. He has not once conceded that parts of the left with which he has long associated have a problem with antisemitism. When challenged recently on why he backed the creator of a vile antisemitic mural on Facebook in 2012, his spokesman initially said it was “on the grounds of free speech”, only later adding that he did not look closely enough at the image to realise it was antisemitic – a shocking response. And he has failed to condemn party members who have threatened to deselect MPs who attended a demonstration against antisemitism in the party.

Corbyn’s, at best, lacklustre approach was in evidence in his response to Christine Shawcroft’s actions last week. Shawcroft, a Corbyn ally who was responsible for overseeing Labour’s disciplinary process, called for the reinstatement of Alan Bull as a council candidate in Peterborough. Bull had been suspended for posting several posts, drawing on antisemitic tropes, on Facebook, including Holocaust denial, but only after it was picked up by the press months after two councillors made a complaint. It has since emerged that Bull was endorsed as a candidate by the leader of the local Labour group, even though he had seen Bull’s posts. Shawcroft only resigned as head of Labour’s disputes panel after her email was leaked to the press, and finally quit the party’s national executive committee last night. She had said “this whole row is being stirred up to attack Jeremy”.

This is only the latest episode. Ken Livingstone remains suspended from the party for his comments about Hitler and Zionism. Jackie Walker, former vice-chair of Momentum, has been suspended for saying Jewish people were the “chief financiers” of the slave trade. Len McCluskey, head of the UK’s biggest union and a Corbyn ally, talked of accusations of antisemitism within Labour as “mood music created by people trying to undermine Jeremy Corbyn”.

This has been too common a response from the left: to argue claims of antisemitism are being “weaponised” by Labour’s opponents. So what? It is not for those who have committed grave failings to speculate on the motivations of those who call them out. And any hint that the Jewish community itself might be politically motivated in protesting against antisemitism in Labour is itself antisemitic.

The truth is this: over recent years, evidence of antisemitism has frequently been found within the party and the current leadership has done nothing like enough to address it. Why is that? Until they answer, then Labour will continue to be charged, rightly, with harbouring antisemitic voices.

The Macpherson inquiry defined institutional racism as “the collective failure of an organisation to provide an appropriate and professional service to people because of their colour, culture or ethnic origin… seen and detected in processes, attitudes and behaviour which amount to discrimination”. Corbyn has promised a “zero tolerance” approach to antisemitism. But words without deeds are meaningless.

The home affairs committee was damning about Labour’s disciplinary processes 18 months ago, and criticised Chakrabarti’s recommendations as insufficient. The Shawcroft incident shows these problems still exist. Enough is enough: will Corbyn accept the left’s problem with antisemitism and reform Labour’s approach to dealing with it? The answer to that question will be paramount in determining whether the party, with its proud anti-racist traditions, can successfully defend itself against the charge of institutional antisemitism.