Fillon lost what many considered a certain victory after a newspaper report claimed that he orchestrated a fake parliamentary assistant job for his wife that saw her paid hundreds of thousands of euros (dollars) in public funds.
A ruling will be handed down on June 29 after a trial in which Fillon vigorously denied the claims, saying he was the victim of a political hit job.
The scandal flared anew this week after it emerged that the former head of France's Financial Prosecutor's Office (PNF) told lawmakers she had sustained “pressure” and “very strict oversight” aimed at bringing charges quickly against Fillon.
Fillon's supporters seized on the comments as proof that the prosecutor's superiors, possibly acting at the behest of justice ministry officials, had infringed upon the judiciary's independence to speed his downfall.
He was charged six weeks after the fraud claims emerged in the Canard Enchaine newspaper, an unusually swift move in a country where legal inquiries can take months or years.
The top Paris public prosecutor denied exercising any undue pressure, and on Friday the former financial prosecutor, Eliane Houlette, tried to walk back her statements, saying she “regretted” that they had been “distorted or misunderstood.”
But the uproar prompted Macron's office to say late Friday that the president had asked France's judicial watchdog, the Supreme Judiciary Council, to investigate the claims.
“These statements, which have provoked a significant outcry, have been interpreted as showing that pressure could have been put on the judiciary during a critical moment in our democratic process,” the Elysee Palace said in a statement.
“It is therefore essential to remove all doubt on the independence and impartiality of the justice system in this matter,” it said.
Prosecutors have asked the Paris court to give Fillon, 66, a five-year sentence, with three years suspended, as well as a three-year suspended jail term for his Welsh-born wife Penelope.
They accuse Fillon of paying his wife 613,000 euros net ($700,000) in public money over 15 years for a fictitious job, saying the couple produced no solid proof she ever carried out any significant work.