François Fillon may face legal proceedings this week over charges he wrongfully employed his wife and children while a senator.

Financial prosecutors investigating the case are thought to be planning to bring charges against the couple or open a criminal investigation later this week, according to unnamed sources cited by the Journal du Dimanche.

The paper claimed Mr. Fillon’s lawyers have now lost hope that charges will be dropped. However, the prosecutor’s office has downplayed the report, saying “No decision has been taken at this stage of the inquiry” adding that “no time-frame has been set so far”, The Telegraph has reported.

Right wing and centrist political figures have rallied behind Mr. Fillon, accusing the judiciary of interfering in the election by launching an unwarranted inquiry.

The chairmen of Les Républicans, Mr. Fillon’s party, in both the National Assembly and the Senate joined forces with centrist leaders in the two houses to issue a statement claiming the case against Fillon was “flawed”.

The candidate has vowed to fight on, despite slipping from first to third place in the polls, taking to Facebook in early February to tell supporters “Hold the line. We’ll get through this ordeal together and march on to victory.”

Although he has apologised for employing his family, conceding the practice was no longer acceptable, he has defended himself by pointing out that it was commonplace while he was a senator. He has also hit out at the left, accusing them of running a “very professional slander campaign” to discredit him in the hope of seeing the pro-European Union Emmanuel Macron elected.

Front National leader Marine Le Pen currently tops the polls for the first round of voting, followed by Macron and then Fillon. She is widely expected to lose out to Macron in the second head-to-head round of voting, but Fillon has warned that his supporters are more likely to flock to her.

“If I cannot be the candidate, do you think that Emmanuel Macron will beat Marine Le Pen?” he asked supporters. “No, my voters will go over to Madame Le Pen.”

Le Pen officially launched her campaign last week under the banner “France First”, hitting out at globalisation and Islamic extremism, and vowing to take France out of the EU.

Fillon meanwhile has built his support from a Catholic, socially conservative bloc which grew out of opposition to gay marriage. He pointed out that those supporters are far more likely to back Le Pen’s platform of preserving French culture than they are to vote for a pro-EU, globalist candidate.