On Wednesday, French prosecutors opened a probe into Penelope Fillon who in 1998-2002 was allegedly paid between 6,900 and 7,900 euros (up to $8,500) for working as her husband's parliamentary aide and in 2012-2013 received 5,000 euros gross per month salary at prestigious cultural magazine La Revue des Deux Mondes, owned by Fillon's friend Marc Ladreit de Lacharriere.
"I also know that we have no right to let democracy suffer because of backroom politics. That is why I will fight with all I have. And till the end," Fillon said in an interview to Journal du Dimanche newspaper.
The center-right candidate explained that he and his wife had submitted the necessary documents, mainly paychecks, to the investigators.
On Saturday, French media alleged that Fillon himself had misappropriated some of the funds reserved for his assistants.
On Thursday, Fillon said that he would step down as a candidate if an investigation was opened into him.
The first round of presidential elections is scheduled for April 23.
