A French father who stuffed his son into a washing machine and then surfed the internet as the toddler died was jailed for 30 years on Friday.

Christophe Champenois, 36, rammed three-year-old Bastien into the device and switched it on, allegedly as punishment for misbehaviour.

The child's 29-year-old mother, Charlene Cotte, told investigators she did a puzzle with her daughter, and Champenois used the internet while their son screamed inside the whirring washing machine.

She was jailed for 12 years, for "aiding and abetting murder and violence".

Cotte said that when her ex-husband removed Bastien from the machine and noticed he was no longer breathing, he said: "At least he won't bother us anymore."

It was Champenois himself who called emergency services in the town of Germigny-l'Eveque, east of Paris, in November 2011, saying he had a "small problem" as his son had fallen down the stairs.

Champenois said he had given his son a bath and that the child must have drowned because he had water coming out of his nostrils.

But the victim's older sister, then five, told the doctor: "Daddy put Bastien in the washing machine because he was naughty at school" -- a version she maintained throughout the investigation.

A neighbour who came to the apartment to help described the child as "frozen, completely naked. He was all white, limp, practically like a toy.

Cotte's lawyer Gerard Zbili described her as a "broken woman who lost the child that she loved" but who was unable to protect him out of fear of her husband.

During the investigation it emerged that the golden-haired Bastien was not wanted by his father, who meted out harsh punishments for his increasingly agitated behaviour at home and at school, such as locking him in a cupboard.

Social services had been repeatedly alerted to the family's case.

"This is not an isolated act... it is not a fit of rage or madness, it is the final act of violence against a child who was always mistreated," said Isabelle Steyer, lawyer for a child protection group, who said Bastien has "fallen through all the cracks."