Simon Bridges says not all solo parents receiving a benefit will forced to name the other parent if National wins the next election.
Solo parents - usually women - used to face having their benefits docked if they didn't name the "deadbeat dad". The Labour-NZ First coalition government canned the policy earlier this year, saying it was "discriminatory" and "didn't achieve its initial purpose to get money from the partner".
Research by the Ministry of Social Development published in February found the sanctions "disproportionately affect children already at high risk of persistent poverty", and there was evidence children who grew up in families who had their incomes slashed under the policy were more likely to "come to the attention of the care and protection system".
But National proposed bringing the sanction back in a discussion paper released earlier this week.
"It's both right in practice and right as a value," leader Bridges told Newshub Nation on Saturday.
"It's pretty simple - if you're a dad of a child, I think you have a responsibility to front up and be accountable and responsible for that."
He said "the vast majority of New Zealanders would agree", and took a shot at the Government for singling out this particular sanction for removal, while keeping others the Welfare Expert Advisory Group recommended should go, such as sanctions for refusing drug tests and breaching arrest warrants.
"If it's so good, if it's so evidence-based, if it's so clever, how come the Government hasn't done any of it? I mean, they've literally spent many millions of dollars on it, and they're not doing it."
Bridges said if the sanction comes back, not all will be forced to name the father.
"The reality of this is there will be a host of exceptions - I get that. When you think of situations where there is a danger of violence, of all these sorts of things - we're not stupid, we get that."
There were exceptions under the old policy too - but in 2017, more than 13,500 solo parents were still having their incomes docked after not naming the father.
"The presumption should be they make clear who the dad is - then the dad is accountable and responsible. I acknowledge though there will be exceptions," said Bridges.