An old rule of democratic politics was well expressed by Edmund Burke when he told parliament: ‘I do not know the method of drawing up an indictment against a whole people.’ That was in the 18th century. Today, many are ready to draw up an indictment against a whole people as long as they are Jews.

For decades it has been a given of the left that antisemitism was an expression of reactionary politics. It is. In his memoirs, Geoffrey Howe recalls the ‘malodorous antisemitism’ of Tory MPs at the time of the Westland affair when the Jewish Leon Brittan was in the firing line. Alan Clarke’s memoirs are riddled with antisemitic cracks and asides.

The BNP remains impregnated with antisemitic ideology. The only substantive works written by the BNP boss, Nick Griffin, are accounts of how the British media is secretly controlled by Jews who disguise their origins to control television and newspapers. When those on the extreme right refer to Zionists and Zionism this is barely-disguised code for Jews and Jewishness. To attack the latter using the word ‘Jew’ alerts people to the suspicion of antisemitism. To use the term ‘Zionist’ allows the same point to be made in code.

Yet as the BNP, in its search for electoral legitimacy, tries to bury its core antisemitism (currently by using the proportional voting system to elect members of the European parliament), it is now parts of the left and their allies which have dropped their guard and are beginning to allow antisemitism to re-enter political discourse.

The focal point is not just Israel. Criticism of the wrongdoings of the Israeli state is not antisemitic any more than criticisms of what governments of countries that privilege Catholic or Muslim beliefs and traditions is anti-Catholic or anti-Muslim.

Israeli officials and their supporters may feel frustrated at the lack of interest in the efforts by Hamas, Hezbollah or Iran to see the state of Israel removed from the map of the world, to quote the egregious Iranian president Mahmoud Ahmadinejad. But Tel Aviv has to accept responsibility for what its soldiers do. And although there is little doubt that Hamas demonstrates its cowardice by sheltering its mobile rocket launchers in mosques and schools and uses civilian homes and locations as cover for its terror attacks, the double standard by which Israel is judged is not that of a terrorist outfit but by its own claim to be a rule-of-law, free press, electoral democracy.

So to attack what the government of Israel does is legitimate politics. But what is not legitimate is to turn criticism of Israel into a condemnation of Jews and to paint them again today, as in the past, in negative stereotypes that denies their faith, their birth, their right not to be frightened and their right to support their affiliations and causes.

Alas, parts of the British, European and world left have now thrown in their lot with the rise of a new reactionary antisemitism which, in the name of being opposed to Israel, is unleashing fears among Jews as bad as any since Hitlerism was destroyed.

It cannot be acceptable to march in protest rallies with placards stating ‘Jews to the gas chamber’. It cannot be right to allow slogans to be sprayed in north London saying ‘Kill the Jews’. It cannot be right to firebomb synagogues in London and Paris.

It cannot be right to rewrite history. In 1948, Israel was set up by the United Nations. Britain refused to recognise Israel until 1950. The 1945-1950 era saw many states come into being and massive population transfers. But in 1948, Egypt and Jordan moved to occupy Gaza, East Jerusalem and the West Bank. Far from creating an independent state of Palestine with a capital in East Jerusalem, Nasser and the Kings of Jordan sought to deny the Palestinians their right to statehood.

Yet the left never shouted ‘Nasser, Nasser, Nasser. Out! Out! Out!’ (of Gaza) or told the Hashemite monarchs that they should support the free and independent Palestinian state on the West Bank and half of Jerusalem.

Instead we hear only hate against Israel, as if the country only wanted to occupy forever the lands it has invaded or occupied beyond the borders agreed between 1948 and 1967. Yet when Israel pulled out of Lebanon, or three years ago evicted its settlers in Gaza and left Gaza to the Palestinians, the Israelis’ withdrawal was met not with a turn to political negotiation but to terrorist attacks and a rejection of Israel’s right to exist.

Most in the Labour party will have attended January GC meetings at which Israel was denounced. The death of up to 1,000 Palestinians, some of them children or civilians not connected to the Hamas Jew-killing operation, was horrific. British activists who are Muslims but opposed to jihadi Islamist ideology expressed identity with Palestinians as co-religionists. This is understandable. But horrible as the death toll was in Gaza, why was there not similar outrage when 2,000 Muslims were killed in Gujarat by Indian religious-political extremists in 2002? Why, when 8,000 Muslims were killed by Serbs at Srebrenica in 1995, was there no giant mobilisation by the Stop the War organisers?

But, of course, none of these Muslim bloodbaths have been done by Israel. Serb orthodox Christians, or Indian Hindu extremists, or Sudanese and Iraqi Muslim dictators are allowed to kill Muslims by the scores of thousands and, although concern and outrage is expressed, it is as nothing compared to the full hate of the left that falls on Israel.

What distinguishes Israel from all the other Muslim-killing politics in the world? No prizes for guessing. Ed Husain, author of The Islamist and whose Quilliam Foundation seeks to build bridges between British Muslims communities and other groups, bravely condemned the open antisemitic attacks that took place by Jew-haters who used the anger over the Gaza conflict to attack Jews. His reward was to be attacked by a prominent British Muslim, Azad Ali, who described moderate British Muslims as ‘self-serving vultures feeding on the dead flesh of Palestinians’. Ali also denounced the ‘Zionist terrorist state of Israel’. Ali is not a lonely, marginalised voice. He is a civil servant employed by the Treasury and enjoyed a reputation as a man ready to promote good community relations.

But for Ali, and the many who revealed the depth of their hatred of Jews and contempt for Muslim activists who refuse to join in the rhetoric of Jew-hate, the issue is not Israel but the very existence of Jews.

From Stalin to the Trotskyist groups who denounce the death in Nazi extermination camps of LGBTs but do not mention the Jews, the left has never been able to shake itself free of antisemitism. Boris Johnson apologised for the hurt he caused black Londoners when he described African children as ‘picanninies’. Ken Livingstone could not say sorry after he insulted a Jewish journalist as a Nazi ‘concentration camp guard’. Livingstone can produce all sorts of slippery rationales for his position. But for many London Jews it was proof that the left glossed over antisemitic hurt.

There will be no peace in the Middle East unless antisemitism is removed as a component element in the ideology of those who oppose Israel. The left has to be as tough in denouncing the Hamas charter, with its litany of hate against Jews, as it is tough in demanding more jaw-jaw and less war-war from Israel. If the left is not tough on both antisemitism – and those who wittingly, or not, allow dislike of Israel to segue into a language in which Jews feel frightened as Jews – then it will not have learnt from history. Antisemitism is back as serious politics and the left should oppose it.