"Friendship bullying" is rife among female high school students with nearly half of Kiwi girls saying they have been bullied by their mates.
Research from the University of Auckland has revealed girls are just as likely to be picked on by their friends as by their enemies.
Researcher Dr Ro Lange said 44 per cent of the 1300 Year 10 girls involved in the study had been bullied by friends and more than 85 per cent had experienced at least one type of bullying such as being ignored or excluded.
Dr Lange, who is also a school counsellor, said there were two distinct types of friendship bullying.
Group bullying involved a group ostracising one member; triadic group bullying involved a third person befriending two best friends and leading to an "awful tug of war" that "just devastates the people involved".
In one case a girl's best friend rostered her lunchtimes so she could only sit with other friends on a Tuesday.
It was only with the help of her family that she finally stood up to her best friend - a moment which left her "feeling like God" for making a stand.
Dr Lange found that puberty was part of the reason friendship bullying happened in high school.
While there was "no magic wand solution" talking to a mother or a friend outside of the situation, or getting involved in sport or another activity, often helped.
Secondary Principals' Association president Patrick Walsh was not surprised by the results as female bullying was a "systemic problem" in schools.
"It's coming on the back of recent statistics showing an increase in actual physical violence amongst girls and by girls and also the increase in the use of cyberbullying by girls which there's a huge tendency for now."
He said bullying often tended to be over things like jealousy or boyfriends but wasn't easily fixed.
"Despite out best efforts it tends to be on the increase and regrettably it often tends to result in girls leaving the school because the relationship can't be restored which is very sad."
Meanwhile a separate study, also released yesterday, revealed New Zealand girls are growing up in a "climate of peer-related violence" that is flourishing thanks to technology and the normalisation of verbal and physical aggression among boys and girls.
"Addressing girls' violence is paramount to stopping the cycle of family violence in New Zealand as these girls will be the mothers of our next generation," said social anthropologist Dr Donna Swift.