Penelope Fillon was paid from money available to her husband as a longstanding MP for the central Sarthe region.
The Canard Enchaine, which mixes satire with investigative reporting, detailed various periods during which Penelope Fillon was paid from money available to her husband as a longstanding MP for the central Sarthe region.
Hiring family members is not against the rules as long as the person is genuinely employed, but the newspaper said it had been unable to track down witnesses of her work.
Citing pay slips, the paper said Penelope, who has always been seen as uninvolved in her husband's political life, was paid from 1992 to 2002 from funds intended for parliamentary assistants.
From 2002, when Fillon took up a cabinet post under then president Jacques Chirac, she became an assistant to the man who carried out Fillon's parliamentary duties in his place, earning between 6,900-7,900 euros per month.
The paper said that she was again paid "for at least six months" in 2012 when Fillon, then prime minister, left government after the defeat of rightwing president Nicolas Sarkozy.
"In total, Penelope will have earned around 500,000 euros from parliamentary funds," the paper said.
The paper also claims that Penelope Fillon was paid around 5,000 euros a month between May 2012 and December 2013 by the periodical La Revue des Deux Mondes (The Review of the Two Worlds).
The literary magazine is owned by a friend of Fillon, Marc Ladreit de Lacharriere.
Canard Enchaine quoted the director of the monthly, Michel Crepu, as saying he was shocked.
"I have never met Penelope Fillon and I have never seen her in the offices of the review," he said.
Polls forecast that Fillon, from the rightwing Republicans party, would win presidential elections due in April and May if the vote were held today.
But many analysts see the contest as highly unpredictable with Fillon facing competition from far-right candidate Marine Le Pen, centrist Emmanuel Macron and others.
Penelope Fillon, a native of Wales, is the mother of the couple's five children.