"People like Kim Kardashian are making it quite clear that it's a normal part of courtship and relationships to produce this sort of thing and share it in the context of relationships. But it's also ... quite obvious that when relationships go wrong, or when the recipient doesn't have the kind of honour that you thought they had, then that stuff gets out."
Lyons said there were fears some of the young girls had been coerced, or bullied, into taking the intimate snaps by older men with whom they had formed online relationships.
"We've had reports where young people have entered into semi-anonymous relationships ... with people that they've never actually met but have formed fairly strong bonds with," he said.
"They may have decided to share an intimate image or video ... within the confines of a trust relationship."
The men had then begun blackmailing their young victims.
"[The person] says 'Now I've got this, plus I know your social network. If you don't give me 20 more pictures then I'm going to put this image onto my Facebook, onto your Facebook. I'm going to send it to your mum, I'm going to send it to your school'," Lyons said.
People needed to be aware photos could be circulated if a relationship ended. "When those relationships do go sour, sometimes the person who was the intended recipient may be annoyed and may decide to get some kind of revenge by threatening to share [the photograph] or actually sharing it, or even coercing them back into the relationship in order that they don't share it."
School councillor Sarah Maindonald, New Zealand Association of Counsellors portfolio manager for schools, said she had recently met an underage girl who had been "groomed" to post images online of herself in her underwear.
She also knew of a picture posted on Snapchat showing a teenager "naked or near to" that was circulated around their school.
"They [the girls] might take something that they think is just going to one person and then it becomes public property," she said.
"It has a huge impact on their engagement in education because sometimes they just want to hide away and not be engaged at all. They might start truanting, it can make them unwell, they can get depressed."
While talking to the Herald on Sunday, Maindonald had a group of 10 to 12-year-olds in her office, all of whom said they had been targets of cyber-bullying.
"Certainly, cyber-bullying would be the most common form of bullying we're having to deal with at school," she said.
