Francois Fillon says a judge is placing him under investigation over a fake job scandal – but has vowed to continue his campaign for France presidential election.
For weeks, the center-right presidential candidate has fought allegations that his wife, Penelope, was paid for years for work she did not do.
Francois Fillon called the investigation “a political assassination” against him.
President Francois Hollande criticized his words, and accused him of attacking France’s judicial system.
The president said: “Being a presidential candidate doesn’t authorize you to cast suspicion on the work of police and judges.”
Francois Fillon says he has been summoned to appear before the judge, Serge Tournaire, on March 15.
The date is just two days before the deadline for candidates to submit their final applications. The first round takes place on April 23, followed by a second-round run-off on May 7.
In a combative speech on March 1 announcing the formal investigation, Francois Fillon called on his supporters to “resist”, saying it was up to voters to decide his fate.
“It’s not just me that is being assassinated, it’s the presidential election. The voices of millions of votes have been muzzled,” he complained.
Francois Fillon said he would respect the summons and tell the judge the truth.
The judge has heard several high-profile cases, including those of former French President Nicolas Sarkozy and tycoon Bernard Tapie.
Francois Fillon was selected late last year in national primaries held by the centre-right Republicans that attracted some four million voters.
For a time he was the favorite in the race to succeed Francois Hollande as president – until the fake job allegations emerged.
His appearances have recently been accompanied by loud protests.
He has slipped to third in the polls, behind far-right National Front (FN) leader Marine le Pen and centrist Emmanuel Macron.
Marine Le Pen also faces allegations that she misused EU funds – a claim she denies.
The allegations circling around the Fillon family focus mainly on his Welsh-born wife Penelope.
Le Canard Enchaine alleged Penelope Fillon was paid €831,400 ($900,000) over several years for working as a parliamentary assistant for her husband and his successor, but had no parliamentary pass – raising questions over whether she did the work she was paid for.
Penelope Fillon was also alleged to have picked up €100,000 for writing a handful of articles for a literary journal.
The family has consistently denied the claims. Initially Francois Fillon said he would stand down as a candidate if his case was placed under formal investigation, but recently he insisted that he would fight on “until victory”.
“The closer we get to the date of the presidential election, the more scandalous it would be to deprive the right and centre of a candidate,” he said.
Penelope Fillon also faces a formal investigation, AFP reports, citing a source close to the investigation.