Some New Zealand parents are already threatening to defy any ban on smacking.
The fate of Green MP Sue Bradford's bill hinges on a crucial vote in parliament on Wednesday night.
Under the proposed law, the New Zealand Police Association claims officers will have to arrest offending parents because smacking would be classed as domestic violence.
In 2005 a North Otago mother, who hit her son six times with a cane and four times with a horse whip after he misbehaved at school, was found not guilty of assault. That was because the current law allows parents to use reasonable force to discipline their children.
But if smacking is banned parents who hit their children will break the law.
"I think it's one of those things you do on the spur of the moment without thinking," says one mother, adding she would probably defy the law.
But the Police Association is warning if parents smack and there is a complaint, they will be arrested.
"Anyone who is arrested will be treated the same as anyone else who is arrested for domestic violence. Under current policy, they have to be kept in custody for 24 hours," says Greg O'Connor of the association.
However, police bosses say officers will be able to choose whether they arrest or not.
"I think it's important to do what we've always done which is apply a common sense approach to the law," says Detective Superintendent Gavin Johns, Acting Assistant Commissioner.
The bill consigns the use of "reasonable force" to discipline children to history. But under the new law "reasonable force" will still be allowed in "providing normal daily care". Critics say this is more confusing than the current law.
"The new law, if it came into force, could potentially allow for a greater degree of force to be used against children," says Simon Maude of the New Zealand Law Society.
But anti-smacking campaigners believe commonsense will prevail, adding technically sending a child to their room against there will is kidnapping, and that hasn't led to a flood of arrests.
