The Vatican will open an investigation into French Cardinal Jean-Pierre Ricard, who earlier this week admitted to sexually abusing a 14-year-old girl decades ago.

Vatican spokesman Matteo Bruni said on Friday a preliminary investigation would start once the most suitable person with the "necessary autonomy, impartiality and experience" was found to carry it out.

He said the Vatican was taking into account that French judicial authorities had opened a file on the case.

The Vatican's investigation would not begin in earnest until French civil authorities inquiry had concluded, so that its finding could be used for information.

Earlier this week Ricard, 78, acknowledged the abuse, which he said took place 35 years ago when he was a parish priest.

Ricard, who was bishop in the southwest region of Bordeaux from 2001 to 2019 and was made a cardinal in 2006 by former Pope Benedict, asked for forgiveness and said he would withdraw from his functions and be available for civil and Church authorities.