The campaign of Francois Fillon, the frontrunner in the French presidential campaign, is in danger, after the satirical weekly Canard Enchaîné revealed in its January 25th edition that Penelope Fillon, his Welsh-born wife, was paid €600,000 over eight years for two apparently phoney jobs, one as her husband’s parliamentary assistant, the other as a literary adviser to a magazine owned by a wealthy friend of her husband.

The “central office of the struggle against financial and fiscal infractions” (OCLCIFF), which falls under the Paris high court, announced it has opened a preliminary investigation for fraud and misappropriation of public funds.

Mr Fillon, who served as prime minister to then president Nicolas Sarkozy from 2007 until 2012, had prided himself on a reputation for probity. “There is a social injustice between those who work hard and those who don’t work and receive public money,” he tweeted last September.

Mr Fillon had attacked Mr Sarkozy, who was then his rival for the presidential nomination of the conservative Les Républicains (LR) party, on the grounds that Mr Sarkozy was under investigation in several financial scandals. “Who could imagine Gen de Gaulle under investigation?” he said. (Les Républicains claim to be the political heirs of Gen Charles de Gaulle).

On Wednesday, Mr Fillon said he was “scandalised” by the “contempt and misogyny” of the the Canard report. “So, because she’s my wife, she has no right to work?” Mr Fillon continued. “Imagine for a moment that a politician said, as this article does, that a woman only knows how to make jam. The feminists would scream.”

Mr Fillon made the comment during a visit to his former rival for the conservative nomination, Alain Juppé, who is mayor of Bordeaux.

Mr Juppé was runner-up in the LR primary last November, and would be the logical person to replace Mr Fillon if he should have to abandon his candidacy because of the scandal.

But in 2007, Mr Juppé was banned from public office for a year for his role in a fictitious job scandal at Paris town hall when Jacques Chirac was mayor.

Mr Fillon’s spokesman Thierry Solère told the Agence France Presse that Penelope Fillon “really worked with Francois Fillon”, adding that “Spouses are frequently the collaborators of parliamentarians.”

It is not illegal for French parliamentarians to hire close relatives, on condition that they do real work. Penelope Fillon has always stated her occupation to be housewife.

French law provides for severe punishment for those who have recourse to fictitious jobs. Article 432-10 of the penal code foresees up to five years imprisonment and €500,000 fine.

The anti-corruption group Anticor said it woild file a lawsuit against Mr Fillon if the authorities do not prosecute him.

The scandal broke while the right was gleefully mocking the disorganisation of the socialist presidential primary.

Bruno Le Roux, the interior minister and former head of the socialist group in the National Assembly, said it should be forbidden for parliamentarians to hire spouses or relatives. “When there is an accusation, an explanation is needed,” he told RTL radio. “It’s not the spokesmen who should explain. This is a serious accusation and it’s time for Francois Fillon to give clear explanations.”

According to the Canard, Penelope Fillon received a salary as a parliamentary assistant for eight years. In 2001, her gross pay was €3,900 per month. She continued on the payroll of Marc Joulaud, who succeeded Mr Fillon as deputy for the Sarthe when Mr Fillon became a cabinet minister in 2002.

Ms Fillon’s salary was raised to €6,900, then €7,900 per month during Mr Joulaud’s years in the National Assembly. One of his staff told the Canard she “never worked with” Penelope Fillon and “knew her only as the minister’s wife”.

From May 2012 until December 2013, Ms Fillon also received a monthly salary of approximately €5,000 from the “Revue des deux mondes” which is owned by Marc Ladreit de Lacharrière, a friend of Francois Fillon.

Michel Crépu, the director of the magazine, said he was “astounded” to learn of the payments. “I never met Penelope Fillon and I never saw her in our office,” he told the Canard. She had nonetheless published “two, perhaps three” literary reviews, he said.