Take an elderly anarchist, anti-capitalist, anti-clerical cartoonist and add a suspicion of anti-Semitism and a dash of politics. Into this explosive mix stir several thousand amateur polemicists and a few score professional ones. Now, in a Paris sweltering in the summer heat, light the touchpaper and stand well back.

There is no indication when the blast waves from the Affaire Siné are likely to stop reverberating around France. Already the mayor of Paris, the country's best-known philosopher and the minister of culture have spoken out against Siné, whose real name is Maurice Sinet, while an internet petition in his support has more than 7,000 signatures and is going strong.

Two of the bastions of left-wing publishing - the newspaper Libération and the satirical magazine Charlie Hebdo - are riven by fevered and bad-tempered debate. Every day sees a new avalanche of opinion pieces and web posts and no one expects them to stop soon.

The row kicked off last month when Siné, 79 and ill, filed his weekly satirical column complete with cartoons for Charlie Hebdo as he has done for two decades. Philippe Val, the editor, barely read the veteran contributor's standard ironic invective and so missed the reference made to aspirant politician Jean Sarkozy, the smooth-talking 21-year-old law student son of the right-wing President.

The young man, Siné wrote without a shred of evidence, was planning to convert to Judaism before marrying Jessica Sebaoun-Darty, the Jewish heiress of a huge electronics chain. 'He'll go a long way in life, this lad!' Siné commented. The piece was published without controversy - until several days later, when a radio presenter referred to it as anti-Semitic. The families of those concerned were said to be 'sickened'. Val, who took the controversial decision to re-publish a Danish newspaper's cartoons of the Prophet Mohammed two years ago in the name of freedom of the press, agreed that the piece was offensive and told its author to apologise.

Siné refused, saying he would rather 'cut his own nuts off' and was, more or less, fired. Cue outrage, argument, counter argument, argument. Was the original statement anti-Semitic? For Val, there was no doubt. Siné's statements, he said last week, 'could be interpreted as making a link between conversion to Judaism and social success' and that they spread the old stereotype associating Jews and money.

But for his collaborator and founder of Charlie Hebdo, François Cavanna, they were 'one of Siné's more extreme jokes, certainly dangerous but rare'. Other colleagues supported the cartoonist's 'right to provoke'. Many have signed the petition of support.

At Libération, editor Laurent Joffrin has attacked the anti-Semitism. 'Everything is there,' he said. 'The association of the Jew, money and power in one phrase which stigmatises the arrivisme of an individual.' But at Libération, as at Charlie Hebdo, other journalists disagreed. According to Luc Le Vaillant, a senior editor at the newspaper, Siné is a victim of the 'exploitation of anti-Semitism' in the debate between 'the two sides of the left'. 'It is more than unpleasant to be seen as a potential anti-Semite when you attack the excesses of the American Empire, "the best friend of Israel", when you oppose an [economically] neo-liberal Europe or when you want to do something more than just "regulate" capitalism,' he said. For the row over Siné is about much more than the cartoonist. It is about history and politics.

Both sides have dredged Siné's history of provocation to support their arguments. His defenders talk of his campaigns against French colonialism as well as his 'big gob'. His attackers point to a 1982 radio interview, shortly after a terrorist attack on Jews in central Paris, in which the cartoonist said: 'Yes, I am anti-Semitic and I am not scared to admit it... I want all Jews to live in fear, unless they are pro-Palestinian. Let them die.' Siné later apologised.

'Behind this split are a range of issues, notably the positions taken by the various protagonists on the Israeli-Palestinian conflict,' said Nonna Mayer of the Centre for Political Thought at Paris's Sciences Po University. 'It is complicated and irritating and a lot of stupid, uninformed things have been said. The debate has been tilted.'

Certainly the line-up of those pro and anti Siné pits major figures of the moderate left, such as Paris mayor and potential Socialist Party leader Bertrand Delanoë and philosopher Bernard Henri-Lévy, against those on the extreme left. The latter see themselves as defenders of the right to say what they want without being 'censored' or 'muzzled' by the shadowy 'authorities', 'powers' or even 'networks of influence and capital' that are set on imposing 'savage' 'Anglo-Saxon' capitalist liberal economics on France and on the world.

Other examples of the satirist's humour, cited by Le Monde, include saying that homosexuals smell of the 'shithouse' and that 'pulling the toilet chain is the only choice'. Historical references to French writers who collaborated with the Nazis during the Occupation, the deportation of 70,000 French Jews during the Second World War with the active assistance of the French police and the Dreyfus Affair have also been brought into the row as well as a running discussion in extreme left and extreme right circles about the possibility that Sarkozy senior, the President, is in fact Jewish but hiding it. And it is summer.

'There's a tendency to show off, to enjoy the sound of one's own voice that has fuelled the whole thing too,' said Mayer at Sciences Po. 'It would have been better just to ignore these idiocies. They really do not deserve the attention they are getting.'