Investigative news website Mediapart published what it said were extracts from tapped phone conversations between Sarkozy and his lawyer.
If genuine, they would appear to confirm previous reports that Sarkozy benefited from insider information from a friendly judge about the progress of a case related to an election-financing scandal.
They also reveal that Sarkozy appeared to have a well-placed mole in a senior position feeding him information about a separate probe into alleged financing of his 2007 election campaign by former Libyan dictator Moamer Kadhafi.
The report comes four days ahead of nationwide municipal elections in which both Sarkozy's UMP party and the Socialists are tipped to suffer heavy losses.
Mediapart said it got hold of the summaries of seven phone conversations tapped by judges, which apart from confirming revelations Sarkozy allegedly perverted the course of justice also suggest he received a tip-off from a mole that judges were planning to raid his offices in connection with the Libya allegations.