Nicolas Sarkozy and his wife Carla Bruni on Thursday launched legal action to prevent further publication of conversations secretly taped during his 2007-12 term as French president.
In a move that will inevitably fuel speculation the tapes could contain a seriously compromising "smoking gun", the couple's lawyers said they would ask a Paris court to issue an emergency injunction against further distribution or publication.
The tapes contain hours of Sarkozy's private conversations with Bruni and close aides.
They were recorded by a political advisor, Patrick Buisson, without the knowledge of anyone in Sarkozy's inner circle.
Some extracts -- without any really explosive content -- have already been published, by satirical weekly Le Canard Enchaine and news website Atlantico.
The revelation of what Buisson was doing whilst working as a close confidante of the centre-right president has sent shockwaves through the French political class.
Lawmakers across the political spectrum have denounced what they have described as an unprecedented act of treachery and, in some cases, a potential threat to national security.
In a statement to AFP, Sarkozy's lawyers said the former president and his wife, a singer and former supermodel, had no option but to take legal action.
"The protection of private and secret conversations constitutes one of the foundations of a democratic society and they cannot accept comments made in private being recorded and published without their consent," the lawyers said.
The taped conversations which have been made public so far contain some slightly embarrassing material.
Bruni is heard joking about Sarkozy being a kept man and teasing him that her status as first lady has prevented her from signing lucrative deals to promote wrinkle-creams, unlike actresses Julianne Moore, Julia Roberts and Sharon Stone.
Buisson refers to his boss as "the dwarf" while the former president is also revealed to have been rude about some of his ministers.
Volcanic eruptions, Cuban heels
Neither will have come as a surprise to French voters given Sarkozy's reputation for volcanic eruptions and penchant for Cuban heels.
The ruling Socialist Party have claimed the scandal shows Sarkozy's poor judgement. "He was betrayed, yes. But it was Sarkozy who chose Buisson in the first place," said former premier Lionel Jospin.
Despite the point-scoring, nothing has emerged from the tapes so far with the potential to seriously impact Sarkozy's plan to return to frontline politics in time for the 2017 presidential election.
Buisson, 64, is a former historian and journalist and a self-styled royalist with links to the far right.
He was blamed by many in Sarkozy's UMP party for pushing his boss rightwards and turning him into a divisive figure.
That shift in the latter years of Sarkozy's term is credited by many analysts as being a key factor in his defeat by the Socialist Party's Francois Hollande in the 2012 presidential election.
Buisson is currently being investigated by an examining magistrate over suspicions that his company was illegally awarded lucrative contracts for carrying out opinion polls by Sarkozy's office.
The initial legal action over the tapes is restricted to preventing their further diffusion or publication.
But criminal proceedings could follow and the offences allegedly committed carry a maximum penalty of one year in prison and a 45,000 euro ($61,000) fine.
Buisson has confirmed that he made the tapes but insists he did so purely to help him in his work.
His lawyers say most of the recordings were destroyed and those that survived must have been stolen. They announced Thursday that they would be filing a theft case with police.
How exactly the tapes came into the public domain is an intriguing aspect of the scandal, with some sort of far-right or intelligence services plot amongst the conspiracy theories floating around.
Judicial sources involved in the opinion poll probe deny that any tapes were seized as part of their investigation.
Buisson's estranged son Georges also denied any involvement in leaking them, although he had been aware of the recordings existence at the time they were made.
"He told me at the time they were for a possible book and, if I remember rightly, he said 'they can always be useful'," Buisson junior told Le Point.fr.