After much criticism over the wording of the smacking referendum question Green Party MP Sue Bradford intends to introduce a member's bill in a bid to prevent confusing questions.

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

Prime Minister John Key encouraged people to participate in the referendum despite the tricky question.

"I do think the question is a bit ambiguous and could be read a number of different ways."

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

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

Ms Bradford said the wording of the referendum had been a shock and ambiguous questions should not be allowed.

The Citizens Initiated Referenda (Wording of Question) Amendment Bill required the Clerk of the House to only allow referendum questions which were "not ambiguous, complex, leading or misleading".

Where a question was not allowed a person would be able to re-write it until it meet the criteria.

People who were confused by a question would not vote, Ms Bradford said.

"However, I still believe the strongest statement we can make to demonstrate our commitment to protecting of children from violence it to vote yes in the postal referendum."

It was another member's bill from Ms Bradford that led to the change in the so-called anti-smacking law.