The allegations, which echo those made in 2017 against the wife of former prime minister Francois Fillon, were denied by a source close to Sarkozy who ruled out any wrongdoing.
The investigative weekly newspaper said Cecilia Sarkozy was employed as an assistant to the woman who stood in for Sarkozy in parliament from 2002 when he was promoted to interior minister.
Cecilia took home nearly €3,100 a month in income for the part-time job, the report said, citing payslips.
“Not an article, no report, not one of the many books devoted to the former first lady mentions her work as a parliamentary assistant,” the weekly wrote.
A source close to Sarkozy confirmed to AFP that Cecilia was employed as an assistant to his parliamentary replacement in 2002-2003, but said that her role in her husband's political career was a “matter of public knowledge”.
She was known to have a position advising Sarkozy at the interior ministry and worked on his successful presidential campaign in 2007.
But the report quoted Cecilia telling a TV interviewer in 2002: “I am not paid, the work I do with my husband is voluntary.”
Sarkozy, a conservative, rose from being mayor for the affluent western Parisian suburb of Neuilly-sur-Seine and MP for the area to become interior minister and then president from 2007 to 2012.
Since leaving office after a single term, he has been embroiled in investigations into illegal campaign financing, attempts to influence the judiciary, and taking money from former Libyan dictator Moamer Kadhafi.
He denies all the allegations.
The Canard Enchaine uncovered a scandal involving a fake parliamentary job that erupted a few months before the last presidential election in 2017.
It revealed that long-time Sarkozy ally Fillon had employed his wife Penelope as his parliamentary assistant from 1998 to 2013 without her carrying out duties to justify her salary.
The couple were convicted in June for misusing public funds and handed prison sentences, which they have appealed.
At the time of the scandal in 2017, Fillon and his allies sought to justify his wife's job by saying such practices were common within parliament at the time.
Cecilia Sarkozy, a former model, divorced Sarkozy in October 2007 shortly after he became president and married advertising executive Richard Attias, her third husband.
He too has since married again, to the French-Italian singer and modem Carla Bruni.