New Zealand First's wish to hold a referendum on the anti-smacking law was dropped in coalition negotiations, new Minister for Children Tracey Martin says.

The referendum was an important policy for New Zealand First in the past - it was a bottom line in the 2014 election - but Martin confirmed that it dropped out of the picture in the coalition negotiations with the Labour Party.

"That was one of the policies that did not survive the negotiations," Martin told RNZ's Checkpoint. "So let's move on."

She admitted that she used to smack her children - "a smack on the leg, a smack on the hand" - when they refused to listen to her, but she had not smacked them since the 2007 law change.

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The change removed the legal defence of "reasonable force" for parents who were prosecuted for assaulting their children.

In 2009, 87.4 per cent of voters answered "no" in a referendum on the question: "Should a smack as part of good parental correction be a criminal offence in New Zealand?"

Last week Family First reminded NZ First of its 2014 pledge not to enter a coalition without a pledge to have a referendum on the anti-smacking law.

"NZ First campaigned strongly on fixing the anti-smacking law - an issue important to many families. We will continue to ask them to deliver on their pledge," Family First said in a statement.

Martin said the focus on the smacking law had not worked, and it was time to look at a range of other measures to improve children's safety - such as prevention.