Former French President Nicolas Sarkozy and his wife Carla Bruni are to file a legal complaint over secret audio recordings made of them by an adviser during the 2012 election campaign, lawyers for the couple said on Thursday.
Revelations that Patrick Buisson, part of Sarkozy's inner circle, recorded hours of talks with the conservative leader and his entourage have caused uproar in the opposition UMP party weeks before local elections.
Sarkozy is expected by many to contest the 2017 presidential election after his defeat by Francois Hollande two years ago.
"Mr Nicolas Sarkozy and Mrs Carla Bruni-Sarkozy cannot accept that remarks made in private were recorded and published without their consent," lawyers Thierry Herzog and Richard Malka said in a statement.
"(They) have decided to prosecute, through an emergency proceeding soon to be filed with the Paris Grand Instance Court, the recording and publication of their conversations," they said.
"Protecting the secrecy of private conversations is ... one of the founding principles of a democratic society."
Excerpts of the tapes were published this week in satirical weekly Le Canard Enchaine and right-wing news site Atlantico.fr.
Buisson's lawyer, Gilles-William Goldnadel, said on Tuesday the recordings were authentic. He said his client had made them for historical research purposes and had not intended that they be made public.
Breach of privacy in France carries a penalty of up to one year in prison and €45,000 in fines.
In the published excerpts Sarkozy is heard discussing his electoral strategy and a 2011 cabinet reshuffle, while Bruni is recorded joking about how she had to put her modelling career on ice while she was France's first lady.
"I thought I was marrying a guy with a salary ... I had big contracts and now nothing," she is heard saying, adding that if Sarkozy went on to lose the election she at least could re-activate her career and start selling anti-wrinkle cream.
French media have said dozens of hours of further material could emerge from recordings that date back to 2011.
Goldnadel said the recordings, which Buisson made using a device in his pocket and later uploaded to his personal computer, had been stolen from Buisson and that he would file a complaint for theft against "persons unknown".
"There will be an investigation to determine exactly how these recordings were taken," Goldnadel told BFM TV. He added that his client thought he knew who had stolen them, but did not give names.