More than 350 offences involving suspects aged under 10 were recorded in the Thames Valley region over the past three years, the BBC has found.
Those responsible fell under the age of criminality and cannot be prosecuted.
The 379 recorded offences included a four-year-old accused of a sex attack on a child and a nine-year-old caught in possession of a firearm.
Police said the numbers were going down, while they always sought to speak to parents and use powers like curfews.
The Thames Valley force declined to comment further about the nature of the offences.
The figures, released under the Freedom of Information Act, showed recorded offences by children aged under 10 stood at 91 for 2012/13, compared with 122 in 2011/12, and 166 in 2010/11.
They included the separate cases of a four-year-old boy in High Wycombe and a five-year-old boy from west Oxfordshire who were suspected of sexually assaulting a boy under the age of 13.
Another four-year-old was also dealt with for causing criminal damage to a vehicle in Slough.
Shauneen Lambe, executive director of charity Just for Kids Law, said each child should be dealt with on a case-by-case basis.
She added: "I'm not sure you can fix it [criminal responsibility] at a certain age because different children develop at different rates.
"Criminalising children doesn't help them, all the statistics show putting children in court is not only a terrifying experience but also the outcomes aren't better in their lives. A lot of children doing bad or naughty things need help."
The age of criminal responsibility in England, Wales and Northern Ireland is 10 upwards.
In Scotland, the minimum age is eight, although earlier this month a group of 12 charities called for it to be raised to 12.
They said they were concerned about young children having a criminal record which could affect their futures.