Duncan Garner has admitted he thinks smacking should be in a parent's disciplinary arsenal after refusing to use it on his own children.
Smacking has been back in the headlines recently after a Picton father was taken to court for smacking his child.
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The man, who has name suppression, was discharged without conviction after a complaint was laid against him by the child's mother.
He has been charged under a 2007 amendment to the Crimes Act that removed the legal defence of "reasonable force" for parents prosecuted for assaulting their children.
Massey University professor of humanities Chris Gallavin told The AM Show on Wednesday he didn't think one case meant the law wasn't fit for purpose.
"I don't think that [the case] can be necessarily held to say that the law is an ass as it were," he said.
Garner, who has four children, said he didn't feel right using force as a punishment, but the kids know when it's off the table and misbehave as a result.
He had been smacked as a child, but resisted doing it himself because he said it "didn't feel right" considering the size difference between him and his children.
"It wasn't for me, so it's use your words to the kids. It hasn't been successful over the years, and I think parents are in a weaker position as a result," he said.
"It's much harder to discipline your kids now as a result, kids know this and they run rings around you as a result."