Antisemitism has become “part of the air that we breathe” in France and its various promoters — on the right and left — are coalescing to form a toxic threat to the country’s Jews.

So says Professor Andrew Hussey, director of the Centre for Post-Colonial Studies act London University’s School of Advanced Studies and the author of a groundbreaking study, The French Intifada, published in 2014.

He revealed that his French publisher would not accept the title, instead re-naming it Insurrections En France (“Uprisings In France”), because, Mr Hussey said, “He thought people would talk too much about the Jews.”

Prof Hussey said that currently “there is what is called the ‘new antisemitism’ in France,” which is mainly manifested in the banlieues, the poverty-stricken immigrant neighbourhoods in and around big cities. “There has always been the ‘antisemitism du salon’, or the old antisemitism [as expressed in Vichy] — that will never go away. But then there is the more populist antisemitism as expressed in the banlieues.”

He came across this when he began researching the murder of Ilan Halimi, the young French Jew who was killed in Paris in 2006 after weeks of torture. “I began talking to people in the banlieues in 2008, and it was very contentious politically, because the only person who described it as an antisemitic crime was [former president Nicholas] Sarkozy. The government wanted to put it down to social delinquency and were in complete denial about the antisemitism. I wanted to find out if it was true or not.”

He discovered, after talking to young people and gang members, “antisemitism as a form of youth revolt, despite the fact that they admitted they had never met anyone Jewish”. In the banlieues, he said, “you have a kind of civil war between Jews and Arabs which was exported from Algeria, where they all came from”.

Though there is denial in some echelons of Jewish society, Prof Hussey said “Jews on the ground know it’s real”.

Exploiting this already volatile situation is the controversial French comedian, Dieudonné M’bala M’bala, who has been convicted a number of times for hate speech and glorifying terrorism.

Prof Hussey began his academic studies in Lyons, “which unbeknown to me was fascist central, and which was where Robert Faurisson was a professor”. These days, Faurisson appears on stage in Dieudonné’s shows, dressed in striped “camp” uniform, while the comedian, making the “quenelle” salute — associated with the extremist right — tells the audience, mainly from the banlieues, about the third strand of antisemitism — “négationisme” — or Holocaust denial.

“These kids don’t know who Faurisson is, he’s just an old professor, but he’s also a martyr to them,” said Prof Hussey. “Négationisme is basically an occult conspiracy theory among intellectuals. But it becomes dangerous when it becomes an established, almost religious belief, out in the banlieues. And for these kids, it explains everything: the Jews run the world.”

The “casual antisemitism of youth revolt” found a darker expression in the 2012 killings in Toulouse by Mohammed Merah, who murdered seven people, including three children, at a Jewish school. During a 30 -hour siege after which he was shot dead by police, Merah said he had attacked the school because, “the Jews kill our brothers and sisters in Palestine”.

Mr Hussey did work in prisons after Merah’s killing spree and discovered that he had become “a hero” to prisoners. He also believes that the banlieues and the extreme right National Front, led by Marine Le Pen, have something in common — both despise the concept of the French Republic and both want to dismantle it. “For both of them, after Charlie Hebdo and the Hyper Cacher attacks, the slogan is not ‘Je suis Charlie’, but ‘Je suis manipulé’. (‘I am manipulated, by the government’).”

It was no accident, Mr Hussey believed, that Ms Le Pen chose to launch her presidential campaign in Lyons. “That’s the lodestar of understanding the French political climate. It was the capital of collaboration… and it was also the capital of resistance”.

There is a fourth group that expresses antisemitism: “the Catholic ultra-right, for whom the Jews represent the atheist, modernist, demons.” In anti-gay marriage demonstrations by this group, slogans such as “Mort aux homos, mort aux pieds-noirs, mort aux Juifs” — “Death to gays, to Arabs, and to Jews” — can be seen. “And the other group opposed to the Republic has been the Catholic Church in France.”

In every country, Prof Hussey said, the Israel-Palestine situation had an effect on the local debate. “But when it is downloaded into France, where the stew of antisemitism is so particular, it takes on this poisoned energy. It’s to do with atmosphere. And now, I’m starting to feel that this stuff has long since left the library [and academic research] and become part of the air that we breathe.”