A survey commissioned by lobby group Family First shows almost half of those polled have smacked a child illegally in the past year.
The survey asked 1000 people for their views on the changes in 2007 to child discipline laws which removed the defence of reasonable force for the purpose of correction for any adult accused of assaulting a child.
The survey found that 44% of parents with children under 12 have smacked them to correct their behaviour.
Family First national director Bob McCoskrie says the numbers suggest parents are ignoring the law because it is out of touch with reality.
The margin of error in the poll was plus or minus 3.2%.