Footage of four women goading toddlers to fight has "stunned" police and social services in Devon.
A jury at Plymouth Magistrates' Court was shown the footage
The seven-minute footage, filmed at a house by one woman, was shown in a case at Plymouth Magistrates' Court.
In the clip, a boy wearing a nappy was called a "wimp" for not hitting a girl back after she struck him in the face.
Four women admitted child cruelty charges and were released on bail on Wednesday. Det Sgt Andy Kings said the police had been "shocked" by the case.
"This was a multi-agency operation with the police and social services working together and every professional that has seen this has been shocked and stunned," he said.
"Locally this is something that is new to us, but we are aware that similar incidents have occurred elsewhere in the country and it is something people need to be aware of."
The film was found by social services.
The boy, aged two, is seen crying after being punched in the face by the three-year-old girl and is told by one of the four women in the room "not to be a wimp or a faggot" and to hit her back.
The four women, all from the same family, are heard laughing as the toddlers are urged to keep on fighting.
When the boy tries to get away and climb into an armchair, the women shout at the girl to punch him again.
She does and the boy is urged to fight back, but says: "No, I don't want to."
The girl leaves the room, and when she comes back the two are taunted and told to fight again.
The court heard that when interviewed by police, one of the women said: "I didn't see any harm in toughening them up. I done the same with my own children."
One of the women pleaded guilty to causing or procuring the children to be ill treated in a manner likely to cause unnecessary suffering or injury.
The other three pleaded guilty to jointly inciting the ill treatment of children.
Sentencing was adjourned until 16 March for reports.
The children are in the care of Plymouth City Council's Social Services.