New Zealanders have begun voting on a referendum on whether smacking children should remain a criminal offence.

Three million voters began receiving ballots through the mail on Friday. The vote is open until Aug. 21, and the government will not be legally bound by the result.

The question reads: "Should a smack as part of good parental correction be a criminal offence in New Zealand?"

Smacking was criminalized in 2007 in New Zealand in order to stop the use of "parental discipline" as a legal defence in assault cases.

People in the "yes" camp argue that a vote for their side would give children the same legal protection as adults. Opponents have said a yes vote would criminalize parents.

Some observers have criticized the wording of the referendum question, saying it is ambiguous or even leading. The government has run a number of television advertisements aimed at helping voters better understand the question. 

Critics have also said the referendum, which is priced at the equivalent of $6.4 million Cdn, is a waste of taxpayer money.

Other countries back sparing the rod

Smacking children is a criminal offence in some 24 countries, most of them European.

In early 2004, the Supreme Court of Canada upheld a century-old law that allows parents, teachers and caregivers to spank children. But it ruled that the use of corporal punishment be confined to children between the ages two and 12.

The Senate has tackled the issue repeatedly, most recently in June 2008. The Senate approved a bill that sought to eliminate Sec. 43 of Canada's Criminal Code, which allows parents, teachers and caregivers to use reasonable force to discipline a child and correct their behaviour.

The bill needed approval in the House of Commons to be passed into law, but the House never held a vote.