The remarks which have deepened Labour’s antisemitism scandal – something which barely seemed possible, given the depths it has plumbed already – occur barely 90 seconds into Jeremy Corbyn’s speech.

Speaking about a group of Zionists who challenged Manuel Hassassian, the Palestinian envoy to the UK, after an event, the Labour leader says the following:

“They clearly have two problems. One is that they don’t want to study history, and secondly, having lived in this country for a very long time, probably all their lives, don’t understand English irony.”

Disputing one’s opponents’ grasp of history is one thing. But implying that people born and raised in this country are nonetheless outsiders is an obviously racist and antisemitic trope.

If you doubt it, imagine the furore if a video emerged of Theresa May making similar remarks about Islamists during her period as Home Secretary. Or of Donald Trump telling a similar story about Mexicans. Corbyn and his supporters would be up in arms, organising marches and demanding resignations.

Actually, you don’t even need to imagine a scenario. Just look back at what they had to say about Boris Johnson.

One of the really remarkable things about the Labour antisemitism scandal to date as been the way that the Labour leader has managed to avoid much of it sticking to him personally. Even as the allegations and evidence have piled up, Corbyn has managed to just about maintain the idea that he is not personally antisemitic, but has ‘merely’ spent decades surrounded by antisemites.

Today’s Daily Mail report has demolished that firewall, and that before the Labour leader received personal endorsements on Twitter from the likes of Nick Griffin and David Duke. Corbyn almost certainly doesn’t think of himself as an antisemite, but that isn’t the same thing as not being one.

But it raises the question: what difference will it make? Britain’s Jewish have almost completely abandoned Labour already, but to date the wider electorate hasn’t seemed inclined to inflict a dramatic polling slump on the Opposition. Likewise, Labour MPs have been loud about their outrage for weeks but continue to tacitly endorse the idea of making their leader Prime Minister.

Stephen Bush has explored the difficulties facing Labour MPs contemplating a split in great detail in the New Statesman. But this isn’t just a problem for them, but for all those voters who until now have been prepared to overlook everything wrong with Corbyn for the sake of ousting the Conservatives.

If they don’t push Labour into taking action over this, it will be a bleak indication of what the new standards are for the conduct of British public life.