Under 10s arrested in Avon and Somerset for sex crimes
Eighty-six children aged under 10 were arrested in the Avon and Somerset police area in 2009/10, including four on suspicion of sexual offences.
The force released the figures after a Freedom of Information Act request.
They show that 42 were arrested on suspicion of violence against people and 34 for criminal damage.
Of the four arrested for suspected sexual offences, the youngest was aged six, two were aged eight and another was aged nine.
Children aged 10 and under cannot be held criminally responsible, the force said, but any arrests are still logged.
The police said that Home Office guidelines stated suspected offences committed by under 10s "should be recorded as a crime".
They added that it was possible the suspects were not working alone and that an older child may have been involved.
Lawrence Lee, the former solicitor for Jon Venables, one of two 10-year-olds who murdered two-year-old James Bulger in 1993, said the statistics were "very worrying".
"At 10 it is becoming more and more clear that children do know the difference in right and wrong.
"A lot of children under the age of 10 are committing offences because they know they can't be prosecuted," he said.
Rod Morgan, a former chair of the Youth Justice Board and a professor at the University of Bristol, said that children should not face a court if they cannot understand what is happening.
"We should not be dealing with it through the criminal courts unless we are satisfied that the child is of an age that they have the full understanding that should be involved in a criminal court procedure," he said.