The number of young children needing emergency hospital treatment after being injured by violence rose by more than 20% last year, figures show.
A total of 3,402 children up to the age of 10 were treated in accident and emergency units after violence in England and Wales in 2010, up from 2,814 the previous year, according to data supplied by the units.
Across the wider population, 37,000 fewer people were treated following violence last year compared with 2009 but the rise in the number of children being injured "is a real issue", the researchers said.
Cardiff University professor Jonathan Shepherd said the rise followed an 8% increase the previous year. He warned: "The trend is going on the wrong track."
"The question is why, but it's hard to pin down," he said, adding that recent changes making it more difficult and expensive to take children into care "may be a factor". "There may be children left in risky circumstances where they would have been taken into care before," he said.
The figures, which come before the publication of British Crime Survey statistics later this week, showed an estimated 313,033 people were treated following violence in 2010, 37,000 fewer than in 2009.
Youth violence, injuries to those aged 11 to 17, was down 16.5%, and serious violence was down 10.6%, with 11% fewer men and 8% fewer women injured in violence and being treated in hospitals, the figures showed.
The falls were down to a combination of "better, more targeted policing" and the development of more partnerships between police and local agencies, Prof Shepherd said.
He added that the steady decline in cases of violence leading to hospital treatment in recent years suggested that national economic factors were "probably not influential" as there were no blips during periods of boom or bust.
The figures from Cardiff University, which collected data from 59 emergency departments and minor injury units in England and Wales, also showed that men aged 18 to 30 were at the highest risk of being injured by violence. And violence-related hospital visits were most frequent on Saturday and Sunday, and peaked between May and October, the figures showed.