Anyone under 18 who is caught sending a sexually explicit picture by text message could be prosecuted under child sex laws.
The letter was sent out to schools ahead of the school summer holidays.
Detective Sergeant Jan Rusdale said: “They could end up on the register for a couple of years,”
“When they come to getting a job this would then count against them.”
“We just want to get the message out there that this is a very serious offence. We need parents and children to realise this.”
It is thought more naked images are being sent between teenagers via social networking sites than ever before, as well as by text and mobile phone apps