The number of young children needing emergency hospital treatment after being injured by violence rose by more than a fifth last year.
Researchers at Cardiff University also say a possible factor could be recent changes making it more difficult to take children into care.
Doctors dealt with an estimated 313,000 violent incidents, down 11% in a year.
But for the second year running, the figures saw an unexplained rise in the small number of young children who went to hospital after a violent injury.
The report said that although the number of children treated in the 59 units surveyed was only 615, or 1% of all those treated, the second annual rise indicated that there was a “real upward trend” of injuries to children.
Almost six out of every 1,000 people went to hospital with an injury caused by violence during 2010.
Serious violence affecting young people aged 11 to 17 fell by 16.5% over the year, with 7,738 treated at the 59 units with men between 18 and 30 the most likely to report a violent injury.