I've spent a lifetime studying politicians. I remain fascinated by the way in which those who practise the political arts are able to justify the unjustifiable, and in so doing can appear to turn hypocrisy into a virtue. The deeds and misdeeds of the political classes long ago ceased to shock me. But occasionally I am, if not traumatised, then certainly jolted into bewilderment by a particularly abhorrent political act. The invitation extended to Ken Livingstone by those who order the affairs of the Side By Side school in Hackney falls squarely into this category.

Side By Side is a fantastic school for special needs children from Charedi families. It's a model of its kind, in which children and young people with a range of learning disabilities are educated alongside "mainstream" youngsters.

Although it receives around 60 per cent of its budget from local authorities it is in fact independent, and relies heavily on charitable contributions for its infrastructure and running costs. It has four trustees, one of whom is Rabbi Avrohom Pinter, a former Hackney councillor and an acknowledged spokesman for the borough's burgeoning Charedi community. Pinter is a controversial figure even among Charedim, but there can be no denying that he fancies himself as a smart political operator. I understand that he played a central role in extending to Livingstone the invitation to be the guest of honour at Side By Side's fundraising dinner on February 12.

Livingstone is also a smart political operator. As politicians go he is as slippery as any whose career I have studied. As the last leader of the Greater London Council he expected to be chosen by the Labour Party as its first London mayoral candidate 14 years later. When this did not happen, he ran as an independent - despite an earlier promise not to do so - and won. In 2004, having been readmitted to the Labour Party from which he had been expelled, he ran again, despite an earlier undertaking not to do so.

As I wrote in this column in 2008, his career has been carefully constructed on the basis of a shifting alliance of minorities and malcontents. As GLC leader and MP for Brent East, he cultivated the friendship of whatever groups he felt could deliver him significant electoral support. These included the Irish, the Afro-Caribbeans and the Muslims. They did not include - and have never included - the Jews.

He and Boris Johnson are neck and neck in the polls

When I say Jews I mean Jews - not Zionists. Livingstone seems to have a problem with Jews. Consider. Only a politician calculatingly oblivious to Jewish sensibility would have dared, in 1982, to compare the alleged sufferings of Northern Irish Catholics to Holocaust victims. In 1984, in an interview with the newspaper Davar, Livingstone accused Jews of "organising here in London and throughout Britain into paramilitary groups which resemble fascist organisations". As far as I'm aware he he has never apologised for this outrageously false statement. More recently we must call to mind that in July 2004 Livingstone welcomed to City Hall a Muslim cleric who had voiced his support for the murder of Jews. The following year he publicly insulted the reporter Oliver Finegold - who is Jewish - by likening him to "a concentration camp guard".

Yet this is the man whom the trustees of Side By Side saw fit to invite as the "guest of honour" last month. It's been suggested to me that the invitation was extended for a sound reason: namely that Livingstone hopes to snatch the London mayoralty from Boris Johnson in May, that he may well do so (he and Johnson are neck-and-neck in the polls) and that, therefore, Side By Side - and by extension the north London Charedi community - needs to be seen as friendly towards him and as worthy of such favours as he might be minded, if elected, to bestow.

This seems to me a wretched reason indeed for honouring such a man.

Livingstone knows that Jewish voters helped kick him out of city hall four years ago. At that time I declared, in this column, that I could think of no reason why any London Jew (Orthodox, non-Orthodox, anti-Orthodox, Zionist, anti-Zionist, straight or gay) should vote for him. I see no reason to change this view.

Whoever you vote for on May 3, please make sure that it is not Ken Livingstone.