It's more complicated than the Da Vinci code and worthy of a political thriller, writes Angelique Chrisafis from Paris. But will France ever get to the bottom of the "Clearstream affair" - a corruption scandal that never was, based on a poison-pen letter about crooked bank accounts that never existed?
The French prime minister, Dominique de Villepin, today told French radio and parliament he had absolutely nothing to do with the murky affair, which has been described as a "French Watergate". Mr de Villepin has been accused of using a senior intelligence official in a plot to smear his political rival, the presidential contender and interior minister Nicolas Sarkozy, but he said today the charge was totally untrue, and that he had been the victim of a campaign of "slander and lies".
As the French papers devote pages to the scandal each morning, many observers admit to being completely baffled.
The whole saga began in June 2004 when an anonymous source wrote a letter to a French judge accusing Mr Sarkozy and other politicians and businessmen of holding secret bank accounts with the Luxembourg bank Clearstream. The accounts were said to hold kickbacks from the £1.5bn sale of French frigates to Taiwan in 1991. But the judge soon discovered that the allegations were false and the accounts did not exist.
Mr Sarkozy, then finance minister, complained that the affair had been used to discredit him. A judicial inquiry has since tried to find out who wrote the letter and whether there was indeed a smear campaign.
Both Mr de Villepin and Mr Chirac have denied any role in a plot. Last week, Le Monde published a leak of the sworn testimony of General Philippe Rondot, a retired intelligence officer, which suggested that Mr de Villepin, acting on the orders of the president, had asked the agent to dig up information on Mr Sarkozy. This morning, in Le Figaro, however, Gen Rondot denied this.
Meanwhile, two investigating judges are trying to identify the anonymous letter-writer after several businessmen and politicians (Mr Sarkozy among them) who were wrongly named in the list of nonexistent crooked bank accounts added their names to a case alleging "slanderous denunciation".
Already the defence ministry offices have been raided in the hunt for clues, and the defence minister has denied having anything to hide, while the French media have for weeks speculated that the prime minister's offices, too, could be raided. Mr de Villepin said today he would be happy to answer the investigating judges' questions because he was completely innocent.
Could the Clearstream affair force the prime minister to resign? Having already kept his job after the biggest street protests in decades forced him to scrap a youth employment law last month, Mr de Villepin insists he is standing firm because he has done nothing wrong.
His approval ratings have plummeted so far and so fast that he is only a few points away from breaking records as the most unpopular prime minister in 25 years. But he vowed today that nothing could divert him from his duty to serve France.
