There is no more classic antisemitic trope than the idea of the Jew as agent of a foreign power, lacking loyalty to his 'host' country. Add to that the idea of a Jewish conspiracy and you have a double whammy. In accusing Matthew Gould, the British Ambassador to Israel, of acting not on behalf of Her Majesty's Government but the government of Israel, and of conspiring with the Mossad, Paul Flynn, Labour MP for Newport West, is guilty of an unambiguous antisemitism of a directness not seen from an elected politician for many years. It is good to see Douglas Alexander, the Shadow Foreign Secretary, making clear his disgust at his colleague's remarks. But we need now to see the same from Ed Miliband, who has so far refused to condemn Mr Flynn, despite repeated entreaties by the JC.

But what is most disturbing about this whole episode is that a senior and experienced politician such Mr Flynn can utter words which a neo-Nazi might shy away from speaking in public, and yet have no compunction in defending them when challenged and no conception that he has said anything in any way offensive, let alone antisemitic. There has been a sense for some time in which certain antisemitic themes have appeared to become acceptable in polite society, as if positing a Jewish conspiracy and the issue of dual loyalty is not antisemitic, merely a statement of fact.

The Werritty affair, for instance, might on one level have been about nothing more than Liam Fox's judgment. On another level, however, much of the coverage has been driven by the idea that rich Jews have been part of a conspiracy to impose their agenda on the British government. This development is - to say the least - deeply worrying. Mr Flynn may be a maverick but when mainstream politicians start to posit such views, something is clearly taking root. And that sends a chill down the spine.