Visitors walk between the concrete pillars of the Holocaust memorial site in Berlin Photo: Reuters

This Wednesday we remember the greatest crime ever inflicted by man against his fellow man. Holocaust Memorial Day allows us to reflect on the bleakest chapter in the history of the 20th century. And there is a special urgency in the call to remember this year, of all years – because the shadow of the Holocaust continues to fall over the world today.

Mass murder is still deployed as a political tool by tyrants, from Burma to Zimbabwe. Racism is returning to the streets of Europe, from St Petersburg to Antwerp. And, hard though it is to credit after the horrors of the last century, anti-Semitism is creeping back into the corridors of power.

We know that Nazi ideology still has the power to motivate evil men. From the Swedish fascist who tried to acquire the “Arbeit macht frei” sign which hung over the gates of Auschwitz, to the British fascists of the BNP, there is an ominous resurgence of extremist activity visible across our Continent.

It is because we face a new fascist threat, and because the extremism of the BNP is mirrored in the equally toxic ideology of anti-Semitic groups such as Islam4Uk and Hizb-ut Tahrir, that we need, all of us, to make an additional effort to remember how the Holocaust started. And where it ended.

The history of the Holocaust is the history of a society which blamed the Jews for its miseries, sought to push them to the margins and then sought, literally, to make them vanish from sight. In our time we can see the same trends returning. The calls for boycotts of Jewish thinkers at Israeli universities, the rise in anti-Semitic incidents on our streets, the inflamed rhetoric of vilification which culminates in the Iranian president Mahmoud Ahmadinejad’s call to wipe Israel off the map, are all connected.

As the chief rabbi, Lord Sacks, has so presciently pointed out, anti-Semitism is a virus which mutates. Originally it was the Jewish people’s religious identity which came under attack, and the Church led a programme of forced conversion. Then, as society replaced religion with science as a source of authority, anti-Semitism mutated so that the Jewish people came under attack on racial grounds. Now it is Jewish identity expressed through the right of Israel to self-determination which is the focus of anti-Semitism. Israel, like any state, makes mistakes. Sometimes grievous ones. But many of Israel’s enemies now risk repeating one of the greatest errors of history by infusing anti-Semitism with a new and toxic vibrancy. We see it in some of those who have attached themselves to recent anti-war campaigns, with Britons marching through the streets of London declaring “We are all Hezbollah now” even though Hezbollah is a fascist organisation whose leader is a Holocaust-denier who believes the Jews are “grandsons of apes and pigs”. And we also see the apparent mainstreaming of anti-Semitism in comments such as those of a former ambassador who recently objected to the composition of the Iraq inquiry team because two of its members were Jewish.

When prejudice is unleashed in this way we are all affected. As the chief rabbi has pointed out, what starts with the Jews never ends with the Jews. The Nazis targeted gay men and women, Roma, the disabled and Christians of conscience. The BNP are, similarly, as homophobic, Islamophobic and plain, downright racist as they are anti-Semitic.

History teaches us many lessons, if we are willing to pay attention. And one of the most profound is that the best guide to the health of a society has always been how secure its Jewish community feels. Throughout history the freest societies, from 17th-century Holland to 20th-century England, have been those in which Jewish people have felt safest. And over the ages the surest sign that a country is moving away from liberalism has been a growing prejudice towards the Jewish community, whether Vienna a hundred years ago, Germany in the thirties or Russia in the last decade.

It is because that lesson of history is so important that Holocaust Memorial Day is so crucial. And it is because we must ensure the next generation learns those lessons that the work of the Holocaust Educational Trust is so vital. The Trust provides the tools for schools to communicate the lessons of the Holocaust – so that young people can understand the consequences of allowing prejudice to grow. The Trust provides schools with books, maps, images and artefacts from the past as well as a Bafta award-winning production containing the testimonies of survivors. And two students from every school in the country are given the chance to visit Auschwitz and see the site of mankind’s most terrible atrocity with their own eyes.

As the survivors of the Holocaust grow older and we face losing their vivid living testimonies, so the risk of forgetting grows stronger, and with it the risk of repeating history’s mistakes. That is why the Holocaust Educational Trust’s work has never been more necessary, the lessons of history never more relevant and the act of commemoration never more important. Whatever else may divide politicians, the lesson of the last century is that the resurgence of anti-Semitism requires us all to unite against this most poisonous of prejudices.