Jacinda Ardern wants Bill English's backing for the Government's new child poverty legislation.
"We are reaching out, we will do a bit of consultation with the Opposition and see if we can get some support from them," the Prime Minister told The AM Show on Monday.
"This is the kind of thing that if it only happens with electoral cycles, we won't see the long-term gains."
Ms Ardern, who is also Minister for Child Poverty Reduction, is expected to reveal legislation that will require the Government of the day to set targets for reducing child poverty.
"We'll put the requirements to set targets in law, but not the targets themselves - so that hopefully we won't end up having a scrap about what they look like. We'll actually instead say 'yep, we agree with the principle'."
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By not putting the targets themselves in law, she hopes to get support from National - and has drafted a letter for former Prime Minister Bill English telling him how the legislation will work.
"There shouldn't be politics in child poverty."
New Zealand has signed up to the United Nations' Sustainable Development Goals, pledging to halve child poverty by 2030. But Ms Ardern says the past nine years under National saw numbers "pretty static".
A report released last week found small reductions in child poverty between 2015 and 2016, prior to the then-Government's benefit increases. Ms Ardern put that down to the improving economy.
"We might see in the next measure a little bit of a blip in the benefit changes they made," she added.
The statistics used to track child poverty will likely follow existing international measures. Last week's report - the Child Poverty Monitor - measures poverty in a few ways, including household income and material deprivation.
"If a child is living in a household where they can't provide the basic necessities for the child to thrive; if you can't go to the doctor when you need to; if you're not getting decent meals because of affordability issues then I think most people would say yeah, that's a family struggling," said Ms Ardern.
"But we actually have international measures we can use - most of them are based on your income relative to everyone around you."
On the income measure, the Child Poverty Monitor said 290,000 live in households below the poverty line (60 percent of the median) - more than a quarter of all Kiwi kids.
As for material deprivation, 135,000 go without at least seven basic necessities, and 70,000 are missing out on nine.