Religion and politics are in the news daily. The BBC eagerly reported that God had “told” George W Bush to invade Iraq (although the White House denied it). Pope Benedict XVI recently urged Catholics to play a more active role in politics. Rita Verdonk, the Dutch security minister, plans to outlaw the Islamic burqa. New Labour is trying to pass a religious hatred law that would ban any public criticism of Islam. In Madrid last week the Spanish prime minister opened a high-powered interfaith conference to promote “an alliance of civilisations”.

Not a day passes without our having to hear the tirades of “abu” this or “sheikh” that. Londoners live in imminent danger of being murdered by the equivalent of 19th-century nihilist “pests” and “devils” who haunted the imaginations of the novelists Joseph Conrad and Fyodor Dostoevsky.

Militant rationalists such as AC Grayling and Richard Dawkins are up in arms, seeking not just to exclude religion from politics but to wipe it out altogether. This secular mindset was evident in the draft European Union constitution in which Europe’s legitimacy was traced from Thucydides, the Greek historian, to the 18th-century Enlightenment, omitting any mention of Christianity.

Those who fear religion associate it with Belfast, Bosnia and the American religious right. They are like Voltaire, the French philosopher, who used to wake up in a sweat on every anniversary of the 16th-century massacre of St Bartholomew’s night when Catholics murdered Huguenots.

Having little historical sense, many do not grasp that Christianity itself promoted the idea that each individual was sacred, regardless of whether he was Greek or Jew, bond or free. That we have civil society at all, separate from the state, is partly because of conflicts like the investiture contest in the 11th century in which the church defended such rights, as it has done into the 20th century.

Christianity helped establish the moral boundaries that separated kings from tyrants; and from Francis of Assisi to the Salvation Army, it has a good record of looking after the disadvantaged. When did you last see a militant rationalist running a soup kitchen? As Adam Michnik, a secular Jewish intellectual, once observed, two Catholic cardinals, Mindszenty of Hungary and Wyszynki of Poland, kept the flame of freedom alive in eastern Europe when people like Michnik had nothing to say. The ultra-Catholic Poles in Solidarity helped to end the communist reign of terror 30 years later.

Religion and politics interact in many ways. For centuries Europe witnessed an alliance between throne and altar, as prevalent in Protestant as in Catholic countries. In much of Europe it did not survive the challenges of liberalism and nationalism (both expounded with a religious fervour) but it is alive and well in Britain’s Anglican establishment. In our own day, too, a puritanical Wahhabist Islam has been used to legitimise the far from puritanical tribal dynasty that rules Saudi Arabia.

Then there are the “political religions” in which a political ideology tries to usurp the claims made by traditional religions, providing a surrogate god and determining who is good or evil.

These phenomena began during the French revolution when the Jacobins (whose name derives from a Dominican convent turned into a club) tried to create a godless religion involving the worship of Reason. Anyone who resisted the Jacobins’ reign of “goodness and virtue” was eliminated like a diseased limb and Paris became a bloodbath. Charles Dickens could still sense the blood in the streets when he went there decades later. A quarter of a million people had been sacrificed for refusing to respect the new revolutionary god.The 19th century spawned various utopian cults. The French diplomat Talleyrand got it spot on as to why most of these failed when he suggested that a cult leader who was not winning many recruits should try being crucified and rising on the third day.

In modern times the Bolsheviks, Fascists and Nazis created successful cults involving the worship of the mummified Lenin, the Italian Duce and the German Führer.

Marxism metabolised Christian notions of mankind’s fall and redemption, although the saviour was the “chosen class” rather than the crucified son of god. There were sacrifices on an enormous scale: 80m people died in the 20th century through confessions, torture, shootings and the gulag to bring about the Marxist-Leninist idea of heaven on earth.

Political religion is still alive and well in starving North Korea, where they are “celebrating” the reign of a communist dynasty with God-like pretensions, a little chap with platform heels and an Elvis quiff being the current object of devotion. Republics such as the United States and France have what are called “civil religions”. The American president gives inaugural and state of the union addresses and appears at moments of great crisis. If you were French, you would also see a lot of Jacques Chirac.

Maybe Remembrance Sunday, in two weeks’ time, is the clearest example of a British civil religion, when we honour the millions who made the greatest sacrifices.

Talk of civil religions happens most frequently at times of danger and division, like the race riots and Vietnam war that polarised the US during the 1970s. Make no mistake, we are in such a time of real and present danger now, and it will take more than the Home Office “citizenship ceremonies” to get us through it.

Rather than scorning the ultra- patriotic Americans, perhaps we can learn from their sophisticated civil religion, which involves more than stars and stripes-waving on manicured lawns. Immigrants to the US become Americans, attenuating other loyalties. Here, we just occasionally get something like David Starkey’s Monarchy on television to remind us where we have come from, a story those who come to live here might be curious to learn.

One thing is still missing, though. Stalin used to remove images of senior figures he had murdered from official photos by changing them into a bush, jacket, lake or sea. That is what we are effectively doing with Christianity, which in metabolised form still determines who we are and shapes political life as we know it.

Michael Burleigh’s Earthly Powers: The Conflict between Religion and Politics in Europe from the French Revolution to the Great War, is published by HarperCollins