"At this stage he [Ventura] has diplomatic immunity, but the Holy See obviously knows about the serious charges against the nuncio, and I have no doubt the Vatican will take the right decision," Loiseau said.
Ventura also faces a "single" complaint filed in Ottawa, the embassy told AFP on Thursday, adding that the complaint has been reported to officials in Vatican City.
According to the Canadian website Presence, which specialises in religious news and first reported on the complaint, Ventura allegedly groped a man in 2008 at the shrine of Sainte-Anne-de-Beaupre in Quebec province.
"If the facts are proven, they are very serious because when you are a religious leader you are supposed to have a moral authority, so I would say that's an aggravating circumstance," Loiseau added.
Ventura previously also served in Brazil, Bolivia and Britain before being appointed papal nuncio to Ivory Coast, Burkina Faso and Niger, Chile and then Canada.
Catholic clerics have been denounced in countries as far afield as Australia, Brazil, Chile, Ireland and the United States, prompting pledges from Pope Francis to rid the church of a scourge that has done enormous damage to its standing.
The pope has vowed that the Catholic Church will no longer ignore abuse allegations, and he removed two prominent cardinals from his inner circle late last year after they were tainted by paedophile scandals.