Supporters of the anti-smacking law passed in 2007 say attitudes towards violence are beginning to change, and more time is needed to see the full effects.
But opponents say enough time and resources have already been wasted, and the law must be changed.
Voters have just three days left to take part in the citizen-initiated referendum, which asks whether smacking as part of good parental correction should be a criminal offence.
A spokesperson for the Paediatric Society, Russell Wills, says the law is contributing to a improvement in people's attitudes towards violence.
But Bob McCoskrie of Family First says the law is a dismal failure because it has not had any effect on the death rate from child abuse.