While an anti-smacking bill was passed in New Zealand in 2007, a new study has revealed the long term damage that could be caused by smacking a child. The study's lead researcher says "smacking is never necessary".
Elizabeth Gershoff was part of a team made up of researchers from the University of Texas and the University of Michigan who looked into the risks associated with physically disciplining a child.
They used five decades of research involving more than 160,000 children to form what they call a "meta-analysis" - an average of all the research to date.
Their conclusions, published in the Journal of Family Psychology, show that smacking is associated with several unintended outcomes. They include mental health problems, lower cognitive ability and a risk of accepting physical abuse as a norm later in life.
Dr Gershoff told news.com.au roughly 80 per cent of parents around the world use smacking to discipline their children. She said they do so for the right reasons but often the outcomes are negative.
"We found that although parents use spanking or smacking with the goal of improving their children's behaviour, it is linked consistently with the opposite outcome. The more children are spanked, the more aggressive and poorly behaved they are. Spanking is also associated with several unintended outcomes."
The research found smacking a child was "associated with more aggression, more anti-social behaviour, more externalising problems, more internalising problems, more mental health problems, and more negative relationships with parents".
Smacking a child was also "significantly associated with lower cognitive ability and lower self-esteem," the study found.
The study concluded there was "no evidence that (smacking) is associated with improved child behaviour and rather found it to be associated with increased risk of 13 detrimental outcomes".
Dr Gershoff said she hoped her findings would be change the way parents looked at the topic.
"Given our findings that smacking does no good for children and instead puts them at risk for harm, I hope that parents will reconsider using physical punishment with their children in the future and seek out positive disciplinary methods.
"Smacking is never necessary and is almost always counter-productive."
She said banning physical punishment is one way to stop parents using it but education is "probably even more important".
"As with parenting itself, we need to teach parents what to do instead, not just tell them not to do something," Dr Gershoff said.
It's not the first time experts have ruled smacking a child can have detrimental outcomes. A Unicef report, released in 2014, found disciplining children with a slap or a smack can threaten their development.
Bernadette Saunders, a Monash University researcher, wrote that physical punishment should not have a legitimate place in children's lives.
"Most parents want what's best for their children, and would not choose to unnecessarily expose their children to any degree of harm or negative influence," she said.