An inquiry has been launched after a garage owner discovered a baby girl living in dire conditions in the boot of a car in the south-western French village of Terrasson.
The baby girl had been forced to live in the boot of a car for over a year, local media reported.
Mechanic Denis Latour, who was carrying out repairs on the car, said the sound of moaning alerted him to the presence of the little girl.
Local media said the baby is between 15 and 24 months old.
Mr Latour told M6 television that she was "naked, completely naked. On this side, there was a crib... a smell, an unbearable smell, the little girl lying on a garbage bag at the bottom of the trunk of the car."
The child, who is believed to have been kept in the boot of the car since her birth, suffers serious delayed physical and mental development, French prosecutor Jean-Pierre Lafite said.
Neither her size nor weight correspond to her age.
There are also psychological and psychomotor problems, with behavioural patterns that do not correspond to the age of the child at this time.
The girl's father told the prosecutor he was not aware of her existence, Mr Lafite said.
A neighbour of the couple, who live in the tiny village of Brignac-la-Plaine and have three other children, said he was unaware of the existence of a fourth child.
The little girl has been taken to a local hospital for treatment.
The parents have been charged with child abuse and neglect.