GWENT recorded 273 sex offences against children including rape, incest and gross indecency in 2009-10, according to figures released today.
Most reports concerned children aged 12-15 years old.
However, five victims in the region were pre-school age and 54 were aged 11 or under.
The figures show, for the first time, the number of young people accused of committing child sex offences.
Nearly 34 of known suspects in these cases were under 18.
Across England and Wales girls continue to be around six times more likely to be sexually assaulted than boys, with over 20,000 (86 per cent) female victims recorded.
The NSPCC used the Freedom of Information Act to obtain this data from all 43 police forces in England and Wales.
The figures show a rise in the number of recorded offences across England and Wales from 20,698 in 2007-08 to 21,618 in 2008-09 and 23,390 in 2009-10.
Home Office figures give no clear picture of how many sex offences are committed every year against children, their ages, gender or whether someone was convicted.
The NSPCC believes this data helps show which children are at most risk and from whom and should allow local authorities and the UK Government to find better ways to protect children.
"NSPCC national head of service for Wales Des Mannion, said: “The rise in recorded sex offences against children is a real concern and we need to find ways to help victims and change the behaviour of young offenders.
“More than 34 suspects in these cases in Gwent were under 18. It’s clear we need more services that address the harmful sexual behaviour of young people, as well as adult offenders.
"This year the NSPCC is launching two UK-wide programmes to help prevent young people from sexually harming others. A third programme will test different therapies for helping children recover from sex abuse.
“We urge everyone to be vigilant and report any concerns they have about a child.”
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