Police are receiving two to three reports every week about Kiwi children and teenagers posting sexually explicit images or footage of themselves online - including children as young as 6.
That rate is increasing and opposition parties are now calling for better resourcing of a specialist police team to tackle online child exploitation.
Detective Senior Sergeant John Michael, the head of the Online Child Exploitation Across New Zealand (Oceanz) unit, told the Herald the reports almost always relate to material that is self-generated - images and videos put up by young people themselves.
"There is usually, on the face of it, no evidence of another party being involved. Behaviours range from naked dancing to essentially really full-on sexualised behaviour - masturbation, that sort of stuff."
Much of the material is put online by teenagers. However, Michael said children were also sharing explicit footage of themselves.
"We are talking 6, 7 [year-olds] - it is really not uncommon for us to get preteens."
The material is most often posted to sites including YouTube, Facebook, Snapchat, Twitter and increasingly on YouNow - a live-streaming site. Those companies are required by United States law to report suspect material to the National Centre for Missing and Exploited Children, which generates a "cyber tip report" that is sent to Oceanz.
In cases involving a child aged 16 or under police officers will be sent to door-knock the family home, to check on the child's welfare and inform the parents or caregivers about what has happened.
Michael said officers followed a well-defined process, given the sensitivity of such discussions and the embarrassment it can cause a young person, sometimes increasing the risk of self-harm. Often by the time a "cyber tip" report is sent to New Zealand the offending material has been removed by a host site.
Oceanz was established in October 2009 and has a team of six, including Michael. The rate of "cyber tip" reports it receives regarding Kiwi kids was flagged in a recently revised and published police four-year plan.
It includes a graph comparing how much police child protection resources are dedicated to online exploitation here and across the Tasman. New Zealand dedicates 0.13 police per 100,000 head of population - less than all Australian states and compared to 0.51 in Queensland and 1.22 in the Northern Territories.
In February the Government announced a $503 million package to boost police officer numbers by 880 over four years. Documents related to that policy outlined the pressure on police and why a boost in numbers was needed, including in areas such as cyber crime and online offending, a "rapidly growing area of unmet demand".
Labour's police spokesman Stuart Nash said resourcing for police work to keep children safe from online exploitation should be "world leading".
"The Government and the police have become very reactive, because of a lack of funding. The pressure goes on about burglaries so the police allocate money towards burglaries. It is all very short-term reactionary."
New Zealand First police spokesman Ron Mark said the resources dedicated to policing online child exploitation reflected an under-funding of police that had occurred for years under National.
"This Government has not been funding the police to do their job. Every mother and father knows how dangerous the net can be, whether they are talking about their grandmother being duped out of money, to child exploitation."
Police Minister Paula Bennett said policing was dynamic, and "needs and demands change regularly".
"It's up to the Police Commissioner where and how he deploys staff to deal with that. Earlier this year the Government announced a $503 million Safer Communities package, which includes a 10 per cent boost in the number of police."
Michael said young people were increasingly connected to the internet, and smartphones and school "bring your own device" policies meant access could be hard to supervise.
"And part of it too is what is considered acceptable behaviour among children and teenagers, and to take a selfie of yourself naked or partially naked and send it to your boyfriend or girlfriend unfortunately seems to be acceptable behaviour. There are a whole range of reasons why this is potentially increasing."
His advice to parents and caregivers was to highlighting the risk, while at the same time realising it is near impossible to monitor a teenager's internet use.
"You have to give them some slack but say at the same time, look guys, just have a think about the possible consequences before you do it."
How police are alerted
• When sites such as YouTube, Facebook and Snapchat are alerted to or detect sexually explicit material involving children or teenagers they are required by US law to alert the National Centre for Missing and Exploited Children. The images will be removed.
• If the young person posting the image of footage of themselves is identified as a New Zealander - such as from information given when a person creates an account - a "cyber tip" report is sent to New Zealand police.
• In almost all cases police officers will be sent to the young person's home to, as sensitively as possible, alert their parents or caregivers.
Sextortion cases involving Kiwi children
The Online Exploitation Across New Zealand (Oceanz) team recently dealt with a "sextortion" case involving a 9-year-old.
The cases occur when a person sends a sexually explicit image or footage to a person, who then demands more images, threatening exposure if the demands aren't met. There are also cases where perpetrators hack into electronic devices to gain access to files.
Detective Senior Sergeant John Michael said they dealt with such cases.
"We have had a case with a child as young as 9. This once again highlights that risk of talking to people online who you don't actually know."
Oceanz works closely with international partners including the National Crime Agency in the United Kingdom. That agency in 2014 was involved in an investigation that resulted in four men being sentenced to a total of 20 years in prison in Bahrain.
Investigations started in January 2012 when a boy's parents contacted UK police, after a person claiming to be a 13-year-old girl from Rome encouraged their son to perform sexual acts via webcam.
Further investigations revealed the "girl" was a front used by the Bahrain offenders, who had targeted hundreds of young people around the world.