Organisers of the recent referendum on the smacking law confronted the leaders of both major parties yesterday - but failed to win a single concession to review the law.

Prime Minister John Key and Labour leader Phil Goff both told a Family First forum in Manukau that the current law was, respectively, "a dog's breakfast" or "a sideshow".

But both refused to change the law despite the 87 per cent "no" vote in last month's referendum on the question, "Should a smack as part of good parental correction be a criminal offence in New Zealand?"

Questions from smacking supporters actually pushed Mr Key into a stronger defence of the law than he has given before, saying the 2007 ban on any use of force against children for "correction" was important to "send a message" that violence against children was unacceptable.

The forum, Family First's fourth annual "Forum on the Family", was also attended by Mr Key last year. Former Labour Prime Minister Helen Clark was the only party leader who turned down an invitation then, and Family First director Bob McCoskrie welcomed Mr Goff's presence yesterday as a sign that Labour had changed.

"You have raised children, you are a Catholic," he told Mr Goff in a question.

But Mr Goff defended Helen Clark as "a committed woman who did her very best for New Zealand" and conceded only that the smacking ban made Labour "look like we were distracted by sideshows".

He said it was time to get outraged by child abuse, and cited programmes Labour had supported to tackle the problem such as Family Start, Project Early and social workers in schools.

Mr Key also used his speech to focus on what he called "the big issues families face", pointing to National's initiatives to provide subsidised jobs and national educational standards and planned anti-drug measures.

But the questions to both leaders were almost all about smacking.

Kiwi Party leader Larry Baldock told Mr Key that the smacking ban aimed to change the way parents brought up their children and "ripped the authority out of our homes".

Mr Key accepted that the law aimed to change parenting, and repeated that the wording was "a dog's breakfast", but noted that it also gave police discretion not to prosecute "minor and inconsequential smacking".

Responding to another question from Mary Paki of Otara, he quoted a school principal in his electorate who told the parents of a Samoan boy in his school report that the boy needed to behave better.

He said the boy's father went to the principal's office the next morning and told her: "You don't tell me how to discipline my child."

To reinforce the point, the father brought the boy back later and asked him to lift his shirt to show "welt marks and blood running down the kid's back".

"That has got absolutely nothing to do with section 59 [the parental discipline law] except to say that we have to send a message through some communities that actually there is a big, big difference between a light smack and violence," Mr Key said.

"That is why the Maori Party got on the phone [after the referendum] and begged me not to change the law."