Statistics obtained by the NSPCC from Thames Valley Police reveal that 1,265 children were targeted - 246 of them below secondary school age - while 69 of them were aged five and under.
Most of the Thames Valley offences - 1,018 - were reported by children aged 11-17 and the figures also revealed that more than 400 sexual assaults against children were reported to police in England and Wales every week last year. Thames Valley police covers Berkshire, Buckinghamshire and Oxfordshire, but county-wide figures were not available.
The NSPCC has obtained figures from the police for the past four years via a Freedom of Information request.
Dan Russell, regional head of service for North London and East of England at the NSPCC, said: "The NSPCC is doing what it can by using information like this from the police to tailor our treatment services - different approaches are needed depending on the age of the child. We are also pioneering new programmes across our region to tackle sexual abuse of children, including our schools service, which aims to visit every primary school in the county over two years, so the young
victims can reduce the debilitating affects of abuse and start to rebuild their lives."
Contact the NSPCC helpline on 0808 800 5000