The French conservative Horizons party suspended 66-year-old Senator Joel Guerriau on Saturday after he was accused of giving a female lawmaker a date-rape drug as part of a plot to commit sexual assault.

Guerriau has been placed under formal investigation on suspicion of drugging a glass of champagne he gave to 48-year-old MP Sandrine Josso with the intention of sexually assaulting her, the senator's lawyer and the Paris prosecutor's office said.

The senator and banker, who has denied the allegations, was formally charged on Friday, and the Horizons party of former Prime Minister Edouard Philippe, which is part of President Emmanuel Macron's coalition, suspended Guerriau as a first step toward his expulsion.

Horizons said it "will never tolerate the slightest complacency towards sexual and sexist violence." The Independents caucus in the French Senate also suspended Guerriau, warning that he could be expelled.

What is known about the case?

Josso, a member of the centrist MoDem party, fell ill after accepting a glass of champagne at Guerriau's Paris home on Tuesday night, prosecutors said.

The two have known each other for about 10 years but are not in an intimate relationship, they added. It was not clear why Josso was at the senator's home at the time of the alleged incident.

Josso's lawyer, Julia Minkowski, has told French media that she fell ill after drinking a glass of champagne at Guerriau's apartment and saw him handling a small plastic bag containing a white substance, leading her to believe her drink had been spiked.

Police searched Guerriau's office and home and prosecutors confirmed that ecstasy had been found. Tests revealed that Josso had ecstasy in her system, investigators said, prompting her to file a criminal complaint.

Guerriau, a senator since 2011, denied any sexual assault plot in a first formal questioning on Friday. The senator "will fight to prove he never intended to administer a substance on his colleague and longstanding friend to abuse her," said his lawyer, Remi-Pierre Drai.

dh/sms (AFP, Reuters)