ou don't have to be a seismologist to harbour a nodding acquaintance with the Richter scale, which is used to describe the intensity of earthquakes. I have sometimes wished that a similar metric existed by which we could describe the strength of anti-Jewish prejudice. Richter measures each earthquake on a scale from 1 to 10. If we were to use a similar metric to describe the current strength of anti-Jewish feeling in the United Kingdom, what score would you give it - and why?

There is always going to be some prejudice against Jews, so we are never going to award a score of zero. A score of 10 might denote a full-scale holocaust. To score higher than six, I would think that there needed to be some degree of official government backing for, and fomenting of, a grass-roots, antisemitic discourse. We're not yet at this point. But we're not far removed from it. I would score it at five at the moment, nudging six.

In reaching this conclusion, I have taken into account not merely the recurrent demonisation of Israel - the Jewish state - in the British media. I've largely discounted calls for BDS from a variety of malevolently-inclined pressure groups. But I've factored into my calculation incidents that would have been unthinkable even a year ago.

One that has made a particular impression upon me was the brutal attack on a rabbi in Gateshead. Several of my Orthodox friends have confessed that they now hide their yarmulkes under nondescript cloth caps or trilbies and I've had reported to me an incident in which a shopper, who may or may not have been Jewish, but who dared to buy items from the kosher section of a supermarket, was followed out and verbally abused. And then there's the saga of the Tricycle Theatre, whose management banned the UK Jewish Film Festival and was only persuaded to change its mind when donors threatened to take their money elsewhere.

We need to ask who is ultimately responsible for this state of affairs - the fostering of a national atmosphere in which these actions can be perpetrated with malice aforethought. Jews will always have enemies. There will always be a certain level of "street" antisemitism, distasteful but of little lasting consequence. It is when this low-life prejudice is harnessed and encouraged by the state that the going is bound to get tough. That's what is happening at present.

Who is responsible for this atmosphere of hatred?

Who is ultimately responsible? David Cameron, Ed Miliband and Nick Clegg.

I accuse Cameron, our revered prime minister, of wanton idleness. He has not done nearly enough to condemn the hatefest with which British Jewry is now confronted. By this silence (for which his being on vacation was a poor excuse) he has in fact encouraged it.

When George Galloway MP declared his Bradford West constituency to be an "Israel-free zone," our revered prime minister should have been the first to condemn him. Instead, he said nothing. When the Tricycle Theatre tried to cancel the Jewish Film Festival, David Cameron remained silent.

Ed Miliband clearly has a problem. He's the Jewish head of a political party that, in its desperate search for ethnic-minority votes, has declared an open season on Zionists throughout the UK.

Like Bruno Kreisky, the Jewish chancellor of post-war Austria who insisted on proving his loyalty to his country by denouncing Zionism, Miliband lost no time in condemning Israel's reaction to Arab rockets as "unacceptable and unjustifiable." Him I accuse of calculated political cynicism.

But my harshest words are reserved for Deputy Prime Minister Nick Clegg, a political lightweight who, purely through the vagaries of the electoral system, found himself in the enviable position of being the kingmaker (so to speak) after the last general election.

At the next such election, just nine months away, the LibDems are facing wipe-out. In a desperate search for votes, Clegg has also decided to play the anti-Zionist card. He has failed to silence the loudmouthed anti-Zionist LibDem MP for Bradford East (David Ward). And he has encouraged his party colleague Vince Cable to threaten Israel with an arms embargo.

He has, in other words, tapped into Britain's anti-Jewish subculture from the basest of electoral motives.