The five-year-old boy, from County Durham, who took an intimate snap of himself and sent it to another child on an iPad. File picture: Stephen Lam/Reuters

London - A boy of five has become the youngest person in Britain to be investigated by police for sexting.

The scale of the epidemic of youngsters sending sexually explicit pictures via phones and computers emerged on Tuesday in new police figures.

They show the number of children being investigated for sexting has increased more than 20-fold in three years.

Since 2013, police have looked at 4 305 cases in England and Wales where primary school children have taken and sent intimate or naked pictures of themselves or others.

Nearly 400 under-12s were spoken to by police. The youngest was the five-year-old boy, from County Durham, who took an intimate snap of himself and sent it to another child on an iPad. The boy and his parents, who have not been named, were spoken to last year but he was not prosecuted due to his age.

The Durham Constabulary also looked at cases involving two seven-year-olds. The figures, released under Freedom of Information laws, show that while police examined 53 child sexting cases in 2013, in the past year the number of investigations into under-12s soared to 1 175 – a 22-fold increase.

Police and children’s charities are concerned that the age of those being drawn into sexting is getting ever younger.

The figures show one boy of ten, only just old enough to have reached the age of criminal responsibility, was cautioned by Northumbria Police for sexting. The boy sent an image of himself to an 11-year-old using Oovoo, a free social media video and image sharing app.

Greater Manchester Police recorded the highest number of child sexters, with 695 cases looked into, including four seven-year-olds and four eight-year-olds. The shocking statistics, which emerged from Freedom of Information requests by BBC Newcastle, showed the practice was widespread, with investigations into primary school age children both in rural areas and in major cities.

It is illegal to possess, take or distribute indecent images of someone who is under the age of 18 – even if the image is of yourself. Many children have reported instances where an image has been shared with a girlfriend or boyfriend, only for it to be circulated on the web, where it could end up in the hands of paedophiles.

Even if the child consented to their image being sent, the sender or receiver can be prosecuted as a sex offender.

Last year a survey of teachers by the NASUWT union revealed more than half were aware of incidents of sexting at their school – some involving pupils as young as seven.

According to research by Barnardo’s, last year police recorded 9 290 accusations of sexual offences where both the perpetrator and victim were under 18, a 78 percent rise on 2013.

The charity did not divulge the nature of the alleged sexual offences, but many are believed to relate to sexting. In 2013, a Childline poll found six in ten teenagers have been asked for sexual images or videos.

Kerry Smith, of Plan International UK, which works for children’s rights, told the BBC’s Victoria Derbyshire programme: "Girls are being pressured – sexting is a gendered issue – more girls are being asked to share.

"There are double standards. When they do [share], the girls are shamed, not the boys who are holding the phones or the pictures or asking for them."

Chief Constable Simon Bailey, National Police Chiefs’ Council lead for child protection, said it was important not to view sexting as harmless teenage behaviour. "There are significant risks involved for children and young people; once an image is sent, control is lost, and it can cause significant distress when it gets into wider hands," he said.