The girl, thought to be aged between 14 months and 2 years, was found shivering and severely dehydrated, lying in her own excrement and urine.
It is feared that the girl had been living in the boot since birth, though the mother-of-four did not give any reasons as to why this was the case.
Speaking about the moment he made the discovery, mechanic Guillaume Iguacel explained that he heard “strange noises that sounded like moans” coming from the rear of the vehicle.
The Portuguese woman, 45, claimed the noises were ‘toys’, but when the men opened the boot, they discovered a small, feverish child lying naked in the boot.
‘I’m still having trouble sleeping, it was a horrifying sight, seeing this little girl in her own excrement, not able to hold up her head, white as a sheet,” Iguacel said.
Mr Iguacel said the girl’s mother appeared to have little concern for her daughter.
‘We were deeply shocked because she didn’t find this abnormal. We told her to remove the little girl (from the boot) and give her something to drink right away,' he added.
The woman, known only as Rosa-Marie, told police she had kept the baby a secret from her husband.
The couple appeared in court charged with child abuse and neglect, and face a maximum sentence of 10 years if convicted.
Jean-pierre Lafitte, prosecutor in the case said:
'I recall seeing her several times a week with her car parked in a little lot'
‘It appears the child had been hidden from her birth, and even worse is seriously retarded.’
He added that the girl’s height, weight and mental development didn’t conform to her age, and she was unable to speak.
Neighbours expressed shock at the discovery, with one by the name of Pascal revealing:
'I recall seeing her several times a week with her car parked in a little lot about 200 metres from her house.
‘But we couldn’t see what she was doing in the boot. We never heard a single cry, never saw a bottle or a pushchair.
The young girl and her siblings- a four-year-old girl and two boys aged nine and ten, are now in the care of social services.