Neither Prime Minister John Key nor Labour leader Phil Goff will vote in the smacking referendum, they said today.

Mr Key said he was "unlikely" to vote because it was an opportunity for the public to speak to politicians.

"On the basis that I'm one of the politicians they're speaking to I never really thought it made a lot of sense to vote."

Other people should participate in the referendum, he said.

The citizen initiated non-binding referendum asks: "Should a smack as part of good parental correction be a criminal offence in New Zealand?"

"I do think the question is a bit ambiguous and could be read a number of different ways," Mr Key told reporters today.

He said questions were one difficulty of referenda and stricter rules may be needed.

Government would change the smacking law if it was not working, Mr Key said.

"There's only been the one now documented case and I'm satisfied that the law is working.

"Often in these cases there are much greater circumstances that don't always surface in the public arena."

Labour leader Phil Goff said he would not vote in the referendum because the question was badly worded.

It was "absolutely" the wrong question, he said today.

"The question implies that if you vote `yes' that you're in favour of criminal sanctions being taken against reasonable parents - actually nobody believes that."

The so-called anti-smacking law was working as it was intended to, he told reporters.

He said most people would not think any response to the referendum question expressed their views and would just not vote.

The question should be: "is the law working satisfactorily?" Mr Goff said.

Maori Party co-leader Tariana Turia said she would be voting "yes", but thought the referendum was a waste of money and the $9 million could have been spent on helping families.

Maori Party co-leader Pita Sharples says his party wants the existing law to stay in place.

Green Party co-leader Russel Norman holds a similar view, saying he will vote 'yes' as it sends a clear signal the law does not have to be changed.

But Act leader Rodney Hide says he will be supporting the referendum, and will vote for parents to have the right to give their children a light smack.