Paula Bennett was unapologetic when asked about a National-imposed sanction that cut income to women and their children if the name of the child's father was not declared.

When asked if she had any apologies to give over the now-scrapped sanction, the deputy National Party leader told Magic Talk: "No, I certainly don't."

Bennett said children deserve to know who their fathers are, and asked why taxpayers should be paying for those children and not their fathers.

"It is not up to others to be paying for other fathers who aren't paying their fair share. I think that is wrong and sends a message that it's up to the taxpayer to pay this bill rather than the parents themselves."

While the sanction was designed to stop fathers from dodging child support obligations, groups like Auckland Action Against Poverty argued it was excessive and punished children rather than the fathers it targeted.

The Government announced in May it would scrap the disciplinary sanction as part of an "overhaul" of the welfare system. The move was suggested by the Welfare Expert Advisory Group, among 42 recommendations.

Social Development Minister Carmel Sepuloni said around 24,000 children would be "significantly better off" as a result of the change, "with many sole parents' incomes increasing by an average of $34 a week".

National was briefed in 2016 that there was insufficient evidence to support the sanction as it "didn't achieve its initial purpose to get money from the partner that's not named in the birth certificate", Sepuloni claimed.

She said removing the sanction would cost $113.4 million over four years. It will come into effect on 1 April 2020.