Can you still be Jewish on the British left? A few months ago, just before the General Election, I wrote a piece about British Jews and their decaying relationship with the Labour party with this question as the headline.

At the time, I felt the headline was somewhat lurid and a bit of a stretch. Yes, there has been a long-term migration of Jews away from Labour and, yes, this trend accelerated alarmingly under the stewardship of Ed Miliband as relations between the party and the community became increasingly hostile.

But there was still plenty of room for Jews to continue their long and proud association with the Labour party. Now, though, Milibandism has ended with a whimper. In its place, it seems, comes Corbynism, and suddenly that question looks all too pertinent.

This became clear at last week's Labour Friends of Israel hustings , which at times became a trial of Jeremy Corbyn's views on Israel. He toned down his rhetoric somewhat, but did little to persuade anyone that he is anything other than an ardent opponent of contemporary Israel, and quite possibly of the state's existence full stop.

His responses to questions over calling Hamas his "friends" and his support for Al-Quds day (at which blatant antisemitism has been displayed) were less than convincing. Corbyn is a man of principle, and his principles do not accord with many in the Jewish community.

Rather unexpectedly, this beardy socialist is now the leading contender to become leader of the Labour party. If he does, it is fair to say that Jewish Labour in this country is all but finished.

Even if he doesn't, the strength of his showing in this election campaign will be a major blow to this already fragile relationship.

But shouldn't Jews base their political allegiance on matters beyond Israel?

Yes of course they should. And for the most part they do. They care a great deal about health and education, economic growth and foreign policy. Israel doesn't define Jewish views on politics in this country, but it does matter hugely to almost every British Jew. Not many choose their party based solely on its approach to Israel but, equally, few would want to belong to a party whose leader openly despises it.

Corbyn represents a strand of the left that few Jews feel comfortable with today.

At the hustings he mentioned that his mother was there at Cable Street with the Jews to stand against Mosley's fascists. This was supposed to illustrate his passionate, ancestral opposition to antisemitism. But it also illustrated just how far apart the left and the Jews have drifted since that moment of unity in 1936.

Around the time of Cable Street, as many as 80 per cent of British Jews voted for Labour. It was the natural party for a group of eastern European immigrant workers to support.

But in the 2010 general election, the Jewish vote for Labour was just 21 per cent. This figure may well have fallen even lower in 2015. We know that seats with many Jewish voters, such as Finchley and Golders Green, Hendon and Harrow East returned solid Tory majorities, despite strong Labour campaigns.

At last week's Labour hustings, several of the candidates lamented the decline in relations between the party and the community, but none of them really offered any insight into what has gone wrong.

This trend has a number of causes. Under Ed Miliband, many Jews felt that Labour was no longer the party of the aspirational middle class, as it had been under Tony Blair. As have many in the country, they came to doubt Labour's economic competence. Miliband's Labour party sought to tax wealth, in the form of expensive houses, which played terribly in the bagel belt of North London. As time has passed, the Anglo-Jewish community has also become more conservative, more comfortable, more distanced from its radical East End roots.

But the other factor, of course, is Israel, and the related issue of attitudes towards the Jewish community, both of which Miliband's Labour struggled with. It is important to note that this falling out works both ways. The modern left doesn't like Israel much, but supporting Israel has also dragged many Jews further to the right than they might otherwise have gone.

Israel's best friends in contemporary British politics are almost all in the Conservative party, which is where many Jewish votes have ended up.

But this problem is about more than Israel . It's also about a sense among Jewish liberals that they have been betrayed by their fellow travellers.

The left is supposed to stand up for the little guy. The left is supposed to fight racism with its every living fibre. But when antisemitism was spiking alarmingly last year, we didn't hear much from them.

Jewish liberals understand that their fellow lefties will criticise Netanyahu's Israel; they often do it themselves. But they expect those same liberal sentiments to be vehemently expressed in defence of the Jews when they are threatened.

If Jeremy Corbyn hates Bibi, that's one thing, but he'd also better despise the openly genocidal, homophobic, anti-liberal, anti-trade union leaders of Hamas, not describe them as friends and invite them to tea.

To the left, Jews are no longer the little guy, it seems. We have our American-funded iron dome to protect us and so aren't worthy of solidarity.

So vehement has anti-Israel sentiment become in some quarters that many didn't actually seem to mind very much last summer when British Muslims committed acts of antisemitism against British Jews, as though the horrors of Gaza somehow justified it.

In Britain today, support for Israel has become a left-right issue. And so most of the hard left despises Israel by default. For them, it represents part of the Zionist-Corporate-American-Neoliberal-Murdoch-Imperialist-London-New York-Tel Aviv nexus that they regard as ruling the Western world in such a nefarious manner.

Corbyn is one of the most eloquent proponents of this world view. If he wins the Labour leadership, an outcome that has gone from improbable to very possible, then the future of Jewish Labour is in serious doubt. Only two types of people are likely to remain.

Those who consider themselves anti-Israel Jews and share Corbyn's antipathy, and those few who are so tribally Labour they can't bring themselves to leave.

For an airy-fairy sort of Blairite Jewish liberal like myself, the right wing of the Labour party has long been a comfortable home.

I'm not leaving just yet, but it is starting to feel pretty lonely out there.