When you write about anti-Semitism in the Labour Party, inevitably, some of the responses are racist: in my inbox, in my Twitter feed and on Facebook. The antisemitic ones have a wide range of themes: from accusing me of being in the pay of Israel to attacking my own Jewish roots. But they have an Islamophobic cousin that is growing in its frequency and has just one theme: that the real reason for the Labour Party’s anti-Semitism crisis is its Muslim voters. The calculation that Labour has made, or so the argument runs, is that losing support among the United Kingdom’s small Jewish population – which numbers around 300,000 – is a price worth paying for winning over British Muslims, who made up 4.8 per cent of the population (2.7 million) at the time of the last census.

I don’t like to respond to hate speech on Twitter, as exposing fringe ideas tends to boost them as much as to debunk them, particularly as every study has found that fact-checking is largely ineffective. However, the idea has now been given sympathetic houseroom in a variety of mainstream right-wing outlets, in addition to the Economist and the Observer, so an explanation as to why this is false is clearly overdue.

The meme rests on three claims, all of them highly dubious. The first is that anti-Semitism in Britain is largely the preserve of Britain’s Muslim population. The second is that there an electoral bounty to be won for Labour among British Muslims and that the policy offer to do it is increasing anti-Semitism from the Labour party. The third is that anti-Semitism within the Labour Party owes its origins to Labour’s Muslim voters.

Let’s take the argument that Britain’s anti-Semitism problem largely emanates from Britain’s Muslims first. In the autumn of 2017, the Institute for Jewish Policy Research produced a highly detailed analysis of what British people thought about Jewish people, which is worth reading in full. The JPR found that 30 per cent of all British people agreed with at least one anti-Semitic statement, and that the figure rose to 50 per cent among British Muslims.

There are more than 60 million people in the United Kingdom and at most there are three million Muslims. So even by using this very broad definition of what an anti-Semite is, which would mean there were more than 18 million anti-Semites in Britain, British Muslims would make up just one and a half of million of them. It is hard to see how you can argue that the one and a half million are more at fault than the remaining 16 and a half million.

Crucially, however, the JPR did not define an anti-Semite as someone who agrees vaguely with one anti-Semitic statement, arguing that this definition was too broad. They defined the anti-Semitic proportion of the population as those who held “multiple and intense” anti-Semitic views, which they defined as just 3.6 per cent of the population, as a whole. If every British Muslim who holds “multiple and intense” anti-Semitic views were to vanish from the United Kingdom, the percentage of British people holding multiple and intense anti-Semitic views would drop from 3.6 to 3.0 per cent. Again, you simply cannot say accurately or fairly that British Muslims are a major contributor to anti-Semitism in the United Kingdom. It is not true.

What about the argument that Labour views anti-Semitism as a way to “get out the Muslim vote”? There are a couple of shaky assumptions here: the first is that the 0.6 per cent of people in the United Kingdom who are a) anti-Semitic and b) Muslim live in constituencies where their votes are vital in winning or holding power. The second is that 0.6 per cent they are all more preoccupied by anti-Semitism than they are by health, education, crime, Brexit or whatever other issue you might care to name.

And of course neither of these assumptions are true: the overwhelming majority of British Muslims live in seats that are Labour fortresses anyway, so no Labour strategist is planning a path to Downing Street that runs on Muslim voters. And as for the idea that anti-Semitism is a vote-mover even among the 0.6 per cent: all the indications are that those of this group who did vote in 2015 largely voted for Ed Miliband, who is literally Jewish, so it clearly isn’t particularly high up their list of electoral concerns.

Fundamentally, we are talking about a group that makes up a fifth of a group that is already less than five per cent of the country and a still smaller proportion of the actual electorate. Thanks to our first past the post electoral system, it is significantly less electorally significant than Britain’s Jewish population, which is at clustered in seats – Hendon, Chipping Barnet, Bury South, Finchley and Golders Green, Ilford North – that do actually help to decide who forms the government.

Of course, a group doesn’t have to have electoral weight. It could have influence within a political party. That’s the third plank of the idea that Muslims are driving Labour’s anti-Semitism crisis. Writing in the Observer, Nick Cohen describes “political Islamists” as one half of Jeremy Corbyn’s base, with the other half “former Stalinists from the old Communist party and Trotskyists from the remnants of Militant and the Socialist Workers party”.

There are, of course, former members of the Communist Party, ex-members of Militant and of the Socialist Workers Party as well as the odd Liberal Democrat in Jeremy Corbyn’s inner circle. I am, however, at a loss as to who the leader’s office employs who could ever have been described as a political Islamist. Nor are they well represented in my inbox, or Twitter feed: the faces sharing blatant anti-Semitism are white, their names Anglo-Saxon. As for Corbyn’s foreign policy views – which are what drives his stance on the issue – they were formed in the 1970s, at a time when the Muslim population as a whole comprised just 0.46 per cent of the population.

This is not to say that the 0.6 per cent of British people who are both Muslim and hold anti-Semitic views don’t exist. But it is to say that the idea that they hold any kind of influence over the present direction of the Labour party is bunk. The reality is that the Labour Party is run overwhelmingly by the same sorts of people who feel able to be so causal about blaming Muslims for the party’s present trajectory: that is to say, the white middle classes. To suggest Labour’s present discontents have anything to do with Britain’s Muslims is a racist canard, nothing more.