Shocking figures: The annual number of sex offenders under the age of ten has doubled in the last three years.

A four-year child was investigated by police for rape while 800 youngster under the age of ten have sexually assaulted other children in the last six years.

The shocking revelations are a terrifying insight into the child abuse crisis plaguing Britain - with experts blaming internet porn and the sexualisation of children for the rise in offences.

The figures, obtained by The Sunday Mirror, also show that the annual number of sex offenders under the age of ten has doubled in the last three years.

Child protection experts believe the majority of the youngsters will have been abuse victims themselves.

But they are also deeply concerned about the accessibility of extreme online pornography and the effect this can have on children who watch it.

Their comment comes two years after David Cameron vowed to ensure pornography is blocked by internet providers on demand from the householder.

Figures obtained by the Sunday Mirror through a Freedom of Information (FoI) request from 33 police forces across England and Wales showed 776 children aged up to nine had been investigated for sex crimes.

No legal action was taken over the incidents as the criminal age of responsibility in England and Wales is 10.

NSPCC spokesman Jon Brown told the Sunday Mirror: 'These figures may seem hard to believe but, unfortunately, there are cases of children as young as three committing sexual offences.

'These children may well have experienced very severe trauma and abuse themselves. That kind of behaviour won't just have come out of nowhere. They will undoubtedly have been victims of sexual abuse. It's terrible.

'There should be no cases like this. These children are not paedophiles - they are victims themselves.'

Shocking data released by the Metropolitan Police appears to show a four year old was recorded as suspected of committing rape between January and September 2014.

Scotland Yard refused to disclose if the child was a boy or girl.

And officers from Greater Manchester Police dealt with 18 horrific cases of children under 10 raping other children between 2009 and 2014.

Disturbing: In one shocking case revealed through a Freedom of Information request, a nine-year-old girl was quizzed for taking or making ­indecent photos of other children

The offenders included a boy aged six, five boys aged seven, seven boys aged eight and five boys aged nine.

Dozens more children under ten were found to have committed sexual assaults in Greater Manchester, including a seven-year-old girl who sexually assaulted a boy.

CHILDREN MUST BE TAUGHT PORN IS NOT NORMAL, SAYS EXPERT A leading psychologist has claimed not enough is being done to prevent youngsters from watching porn on the internet. Dr Linda Papadopoulos wrote a report for the Home Office in 2010 discussing ways in which children could be protected from exposure to x-rated images. Only a tiny portion of her 36 recommendations were implemented, including the introduction of new age ratings for music videos. Speaking to the Sunday Mirror, she claimed the Government needed to do much more to tackle the problem. Advertisement

A nine-year-old girl was quizzed for taking or making ­indecent photos of other children.

Rape by children at such a young age constitutes penetration of their victim other than sexual intercourse.

The paper said the number of children committing sex crimes had doubled from 128 in 2012 to 254 last year and the figures could be higher as several forces did not respond to its FoI request.

Figures from the Met suggest they recorded a total of 2,823 crimes of all types perpetrated by one to 10 year olds between 2011 and 2014.

But the force warned there were errors in the recording of some its data, citing a rape suspect's age being entered as one and many other ages simply recorded as zero because the suspect's age was unknown to the officer entering the data.

Against this, Donald Findlater, research director at the Lucy Faithfull ­Foundation, warned the statistics were more likely to be the tip of the iceberg as many of the crimes go unreported.

He claimed it was 'tragic' when children as young as three display sexualised behaviour and said there was a lack of services available for such youngsters.

Warning: Psychologist Dr Linda Papadopoulos, above, has claimed not enough is being done to prevent youngsters from watching porn on the internet

The Lucy Faithfull Foundation has produced a guide for parents, teachers and playgroup leaders focusing on children who display sexual behaviour.

Calls and emails to its Stop it Now! helpline have more than doubled since 2004, rising from 110 to 225 last year.

The charity even discussed the sexual behaviour of a two-year-old boy with a concerned caller.

A Government spokesman said: 'The age of criminal responsibility is set at 10 years old. Social services work with the families of children under this age whose behaviour gives cause for concern.

'If a child is found to have committed a serious offence, councils can apply to the Family Court to place the child under supervision, or take them into care.

'They could also be placed under the supervision of a youth offending team for up to 12 months.'