Sarkozy, who was charged two weeks ago with corruption and influence peddling in a case related to his campaign to win the presidency in 2007, claims he is the victim of a "grotesque" set-up. He accuses his enemies of using the justice system to undermine a possible political comeback.
But according to extracts from tapped calls published by the French daily Le Monde on Saturday, the ex-president appeared to lobby for a job for the judge in Monaco in return for his help on one of six bribery and funding scandals in which Sarkozy is embroiled.
In intercepted mobile phone calls with his longtime lawyer Thierry Herzog — who also faces charges — Sarkozy is alleged to have said, "I will help him (the judge)… I will get him set up," adding, "Call him today and tell him I will sort it out. I am going to Monaco and I will see the prince (Albert)."
The conversations are alleged to have taken place in February this year on a mobile phone the 59-year-old politician bought using a false name.
Sarkozy's lawyer Pierre Haik declined to comment to AFP on the new leaks, the latest in a series of damaging revelations to have hit Sarkozy since he left power.
The senior magistrate at the centre of the case, Gilbert Azibert, has been charged with illegally passing on information about the a long-running political funding scandal involving the billionaire L'Oreal heiress, Liliane Bettencourt.
Azibert did not get the position in Monaco, a principality on the Riviera which is largely dependent on France, and has applied to retire.
In another alleged extract, Sarkozy told his lawyer to tell the judge that he was meeting that day with Monaco's Minister of State (prime minister) Michel Roger and would keep him informed of how it went.
But according to the newspaper, the authorities believe Sarkozy discovered that his "secret" telephone was being tapped and subsequently decided not to ask for the job for the judge.
It claimed Roger confirmed to police that Sarkozy had talked to him on the day of the conversation was taped but had not brought up Azibert or his desire to head up principality's judiciary.
Sarkozy's lawyer Herzog — who faces the same corruption charges as the ex-president — tells his client on the tapes that the judge had "access to unpublished information" on the Bettencourt inquiry and that he has "worked really hard" to help them.
Under French law it a crime to promise a public position as a favour, whether or not the position is given to the person.
A poll earlier this month showed that two out of three French voters are against a comeback by the charismatic right-wing leader, who is married to the singer and former supermodel Carla Bruni.
The survey for BFMTV, however, found that 72 percent of supporters of Sarkozy's UMP party backed a return.
In the wake of the charges, Sarkozy insisted that "there was no question of renouncing politics" and said he would not decide whether he would stand for the leadership of the party until August or September.
France's Socialist government has rejected claims that Sarkozy is being dragged through the courts to derail his thin-veiled ambitions to stand again for the presidency in 2017.
In a pointed riposte to Sarkozy's allegation, government spokesman Stephane Le Foll said: "The judiciary is independent, there is no longer any interference."