Story highlights Francois Fillon under investigation

Candidate has rejected several calls to stand down

Paris (CNN) François Fillon's scandal-hit campaign to become France's next president took another blow Tuesday when he was placed under formal investigation on multiple counts, including embezzlement of public funds.

The 63-year-old, who has rejected numerous calls to stand down as the Republican nominee, is now likely to face increased pressure over his position.

Fillon has been heavily criticized for failing to quit the race since becoming embroiled in a parliamentary scandal over claims that he paid his wife and children for work they did not do.

Tuesday's announcement, by the National Financial Prosecutor, caps a troubling few days for Fillon. He was forced to apologize for an anti-Semitic tweet sent out by his party earlier this week, and the Journal du Dimanche newspaper alleged that he received a number expensive suits worth thousands of euros from a mystery benefactor.

It said he had received almost 50,000 euros worth of suits and clothing since 2012.