A boy and his parents have been questioned after he sent an intimate picture of himself to another child, a Freedom of Information request has found.
BBC Newcastle discovered that the child, aged just 5, has become the youngest child in Britain to be investigated by the police for sexting.
It is part of the growing problem of sexting, which has become more common among teenagers and pre-pubescent children.
Sexting is defined by the National Society for the Prevention of Cruelty to Children (NSPCC) as "the exchange of sexual messages or self-generated sexual images or videos through mobile phones or the internet." It is illegal to create, possess or distribute sexual images of minors even if of oneself.
Since 2013, more than 4,000 children have been dealt with by the police, and in the last year, nearly 500 primary-aged children were investigated.
A small number of those children aged 10 and over have been cautioned by the police or have been placed on the sex offenders register.
Helen Westerman, Campaigns Manager for the NSPCC, said the organization was concerned about the number of people involved in sexting activities.
She said: "For some children it will be a voluntary action; a risk or a dare, something that they want to do.
"For other children, they've been coerced into doing it. They may have been put under pressure by friends or peers or partners—and actually once that image is out there, it's out there forever, and the effects on that child can be devastating."
She also encouraged parents and guardians to speak to their children "as soon as they have their own devices" to warn them about the taking and sharing of explicit images.
Northumbria Police and Crime Commissioner Dame Vera Baird expressed sympathy for children whose images have ended up on the internet and then bullied for it.
She said the damage that can be done to individuals is "pretty awful," and that sexting itself is "highly dangerous".
Dame Vera also said her force had told teachers to warn children against sexting, saying "because it's a crime, it's a very strong and a very easy message to pass on."
Last year, a mother told The Telegraph how her daughter was emotionally traumatized after she sent an explicit image to a boy who then shared it with his friends.
"After a few days, Kate was a husk; she had barely slept, and was still breaking down in tears."
She added: "In days, she'd gone from a happy, confident teenager to a broken wreck."
The mother said a contributory factor was the availability of pornography to young people, adding that boys who grow up watching pornography think it's normal to pressure a girl into sending them inappropriate photographs.
There have been recent calls for more sex education in schools to combat sexting, but sociologist Frank Furedi has questioned the idea.
He said: "Sex education is not an effective medium for achieving this objective. A far broader approach promoting a culture of learning is needed."
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