PARIS — Kristin Scott Thomas, Andre Dussollier and Sergi Lopez will star in helmer Laurent Herbiet’s “Vatican, le Christ habite chez les Borgia” (Vatican, Christ Lives With the Borgias), exploring the hidden world of the Holy See.

The €9 million ($11.3 million) political thriller is set up at Paris-based Loull Prods., the outfit recently launched by Xavier Castano, who produced Jean-Jacques Annaud’s last three pics. Conchita Airoldi of Italy’s Urania Pictures is collaborating on the film.

It’s co-penned by French investigative journo Michel Desprats, Nathalie Hertzberg, Herbiet and Christian Roux, in collaboration with Italian journalist Gianluigi Nuzzi, author of “His Holiness” and “Vatican SpA,” who’s at the heart of the “Vatileaks” scandal.

Herbiet’s fact-based film will shed light on the power struggle and alleged money laundering within the Holy See, as well as Pope Benedict’s relationship with his ambitious personal secretary.

Scott Thomas will star as the mother of Cedric Tornay, a 23-year-old Swiss guard who

was found dead next to Alois Estermann, who had just been appointed Commander of the Swiss Guard, and Estermann’s wife in 1998.

Tornay was accused of the double murder before committing suicide. Scott Thomas’ character — who’s “as resourceful and tenacious as Erin Brockovich” according to Castano — is convinced of her son’s innocence and leads her own probe within the Vatican.

Castano told Variety he envisioned the film as a sprawling, eye-opening political thriller in the vein of Costa-Gavras’ “Z” or Michael Mann’s “The Insider.”

“We’ve been doing extensive research for three years to make the script stick to reality as much as possible,” said Castano, adding he even sent Desprats and Hertzberg to Rome where they interviewed local guards, journalists and judges.

The producer is casting a high-profile Italian thesp for one of the lead roles and is in advanced negotiation with a French outfit, which will handle distribution in Gaul and international sales.

Pic will mostly lense in the French language and will start shooting next June, in Switzerland and Rome.