Labour leader Phil Goff says the anti-smacking law does not need to be amended or revoked.

Mr Goff caused confusion this morning when he was asked on TV One's Q and A programme whether he thought a smack should be allowed as part of good parental correction.

"Well my answer to that is no, it shouldn't be a criminal offence or we should not have people following up and prosecuting parents for a smack in that context, but remember 110 out of 122 MPs voted for that legislation including every member of the National Party."

That response sparked Family First, who oppose the law, to put out a statement welcoming the apparent u-turn.

Act MP John Boscawen has drafted a member's bill to allow parents to use a light smack to correct their children and Family First director Bob McCoskrie said Labour should now back the Act MP's bill.

But Mr Goff said neither his position nor Labour's policy had changed.

Labour supported Green MP Sue Bradford's bill to remove the statutory defence of "reasonable force" to correct a child, meaning there would be no justification for the use of force for that purpose.

The "reasonable force" defence had been used by parents who had beaten their children with whips and pieces of wood but opponents said the change would make criminals out of parents who lightly smacked their children and removed their right to discipline them.

The bill was hugely controversial and even though it passed in May 2007 by 113 votes to eight, Labour took the flak for it. National backed the bill after a last-minute compromise to add a proviso stating police had discretion not to prosecute complaints against a parent if they considered the offence to be inconsequential.

Mr Goff last night said the law was working.

"We voted in favour of the legislation but there was an understanding all the way through that good parents would not be prosecuted for lightly smacking their child ... and there has been no prosecutions of parents in those circumstances."

Mr Goff said Labour had never supported parents being prosecuted for a light smack.

"That's not a u-turn, that's the policy we talked about at the time."

Mr Goff did not accept his comment was confusing and said he was happy with what he said.

"Technically it is a criminal offence ... the point we are making is there should be no criminal prosecutions of parents in those circumstances.

"I don't think the law needs to be changed.

"There's not a question of backing John Boscawen's bill. If good parents are not being prosecuted for lightly smacking their children then the law is working as intended."

Former Deputy Prime Minister Michael Cullen also commented on the issue in the Sunday Star Times. He said Labour had had to support the bill as it fitted with the party's own policy.

Opposing the bill would have made Labour look unprincipled.

"That was the kind of issue where you're hung for a sheep or a lamb whatever way you go," Dr Cullen said.

He said the law change did not impact on personal freedom.