François Fillon faced fresh controversy on Tuesday over reports he failed to declare a €50,000 (£43,000) loan from a friend, a day after France's mainstream Right unanimously decided to back the conservative presidential candidate despite a damaging financial scandal.
According to Le Canard Enchaîné, the satirical and investigative weekly, Mr Fillon, the candidate for the conservative Les Républicains party, received the "zero-interest" loan from businessman Marc Ladreit de Lacharrière in 2013 but failed to declare it to France's political transparency body.
Under French tax rules, all loans of above €760 must be declared by the borrower.
In 2010, Mr Lacharrière received the highest grade of France's prestigious Legion d'Honneur award, after a recommendation from Mr Fillon.
Last month, Le Canard broke explosive allegations that Mr Fillon had misused public funds to pay his British wife Penelope and children for "fake jobs" amounting to around €900,000.
It also reported that Mr Lacharrière had paid Mrs Fillon €100,000 for writing a couple of articles for La Revue des Deux Mondes, a review he owned.
He has since received a summons by investigating magistrates for March 15 and faces potential charges of influence peddling, misuse of public funds, but also failing to make compulsory (tax) declarations. This final charge refers to this loan, according to Le Monde.
Antonin Lévy, Mr Fillon's lawyer on Tuesday dismissed the latest report, saying that the failure to declare the loan was a simple "oversight" and that he had since repaid it in full, without giving a date.
After facing calls to step down over the scandal, Mr Fillon received the unanimous backing of top party members on Monday, who said any challenge to his nomination was now "over".
Alain Juppé, the former prime minister, also announced he would not replace him should he withdraw.
"The page has turned," Bruno Retailleau, Mr Fillon's campaign coordinator, told Radio Classique on Tuesday.
However, polls suggest that Mr Fillon still faces elimination in round one of the race on April 23 to Front National candidate Marine Le Pen and independent centrist Emmanuel Macron, who is currently tipped to win the runoff on May 7.