If I were Benjamin Netanyahu (and I’m not) I would be thanking whatever gods there be for sending me, at a tricky time, the most useful ally it is possible to imagine in UK politics. To Bibi’s aid has come probably the only man in Britain capable of single–handedly silencing public criticism of the Israeli government’s disturbing new Basic Law, entitled ‘Israel as the Nation-State of the Jewish People’.

If I were a British crusader for the Palestinian cause (and I’m not) I would be cursing whatever gods there be for sending — at a time when it might have been possible to rally critics of this unpleasant eruption of ethno-nationalism in Israeli politics — the most effective British voice available to hamper my argument.

Step forward, Jeremy Corbyn, unwitting ally of the Israeli right, unintending albatross to the Palestinian cause: the man with whose evident anti-Semitism nobody worth listening to would dare risk being associated. Flee Corbyn’s sympathies as from the leper’s bell. Shun his antipathies lest they taint your own.

More than once over the past month, as a columnist, I’ve sat down with the intention of writing for the Times or The Spectator a hostile critique of the Basic Law. This has now — despite strong opposition within Israel and from voices among the Jewish diaspora — been (quite narrowly) passed by the Knesset. But every time I’ve done so, a warning voice has stayed my hand. ‘Now is not the time to voice criticism of Israel,’ the voice has whispered. ‘The only Israel-related issue leading the news media is the anti-Semitism of Corbyn and sinister elements on the Labour left. Touch this subject, and people might hear your argument as an oblique commentary on Corbyn’s refusal to accept the international definition of anti-Semitism. If you suggest there’s something uncomfortably close to racism in a law that conflates nationhood and the state with membership of a single human grouping, people might think you’re on Corbyn’s side. Don’t risk it!’

So I haven’t. Just at the moment, a lot of Jewish people in Britain are feeling desperately sensitive on the subject of anti-Semitism, and you can understand why. The leader of the opposition, the man who aspires to be prime minister — and who will be, if our stumbling government falls and loses an election — is refusing to do or say the simple things that would dissociate him from a poisonous creed that, at its worst, tried to wipe their forebears from the face of the earth.

I’m one of many (I think) who was at first unwilling to accept that Corbyn actually was an anti-Semite. To be honest I’ve found it hard to imagine how anybody could be an anti-Semite: I mean really an anti-Semite, not just someone who laughs at jokes about human types as I can laugh (for instance) at jokes about gays. After the Holocaust (I’ve supposed), anti-Semitism as a serious belief must be dead or dying in Britain.

So for a while I half-believed Corbyn’s accusers were tangling his political views about the Middle East with his personal attitudes towards Jews and Jewishness. Soon, I thought, he would set things straight; go the extra mile in allaying any fears Jewish Labour MPs and other decent people might have entertained about him. But he didn’t, hasn’t, won’t; and I’m a late but now convinced convert to the belief there’s something sick in this man’s mind. He could otherwise so easily have stopped the talk. To have stung even the gentle Lord (Jonathan) Sacks, who as chief rabbi trod a delicate path, into remarking that ‘we have an anti-Semite as leader of the Labour party and of Her Majesty’s Opposition’ is quite something.

So now this business about Corbyn and Jewishness will run and run, and ought to. But should that mean we ought to steer clear indefinitely of criticism of where Israel seems to be going? Here is section 1 (Basic Principles) of the new Basic Law passed by the Knesset by 62 votes to 55:

‘1 — Basic Principles
A. The land of Israel is the historical homeland of the Jewish people, in which the State of Israel was established.
B. The State of Israel is the national home of the Jewish people, in which it fulfils its natural, cultural, religious and historical right to self-determination.
C. The right to exercise national self-determination in the State of Israel is unique to the Jewish people.’

If, in reading that, you replace in the words ‘Jewish’ and ‘Israel’ with (say) ‘Hungarian’ and ‘Hungary’ or ‘English’ and ‘England’ then you get something which I must say would make me feel a bit seasick. Almost half the Knesset seem to have had a similar reaction. Is it wrong to admit to it?

The new law goes on specifically to downgrade Arabic from being one of Israel’s two state languages, calling it ‘special’ instead. Why do that? What is the new law trying to say? What point is it making about the status of Arabs within Israel?

Rabbi Richard Jacobs, president of the Union for Reform Judaism — the largest denomination of American Jews — said: ‘The damage that will be done by this new nation state law to the legitimacy of the Zionist vision and to the values of the state of Israel as a democratic — and Jewish — nation is enormous.’ He added: ‘This is a sad and unnecessary day for Israeli democracy.’

While this draft law was under consideration, it was said that Netanyahu and his political allies were keeping ears and eyes open for international reaction. So, one supposes, were those many Israeli politicians who were unhappy about the proposals, but wondering whether to put their heads above the parapet. If so, they may have noticed the muted response these moves have met in Britain. So far as I can see, the changes have not become an issue here. Netanyahu will have been encouraged by such silences.

For the silence, I do blame Corbyn. The sooner we can get this dirty business of his anti-Semitism sorted out, the sooner Israeli politics will find an honest response from civilised friends here who are uncomfortable, but afraid to say so.