Prime Minister Jacinda Ardern wants National's support for a new law that will "take the politics out of poverty" and bind future Governments to set targets to reduce child poverty.

And she says the Government's families package, which will be launched this week, will lift more than 50,000 children out of poverty and help 70 per cent of low and middle income families.

But National's leader Bill English says the Government can set all the targets it wants for reducing child poverty, but it will not have any cash to lift incomes after its families package comes into effect in April.

Ardern, who is also the Minister for Child Poverty Reduction, said the Government would introduce a child poverty bill in the new year, and she will write to National Party leader Bill English to seek his support.

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It would set a range of measures of child poverty and bind the Government, and future Governments, to setting three-year and 10-year child poverty reduction targets.

"Next year is where we're looking to take the politics out of poverty," she told Newstalk ZB.

"Let's agree collectively on what our measures are and actually have successive governments set some targets."

The range of measures would include ones already used in the Child Poverty Monitor, including a level of material deprivation and severe material deprivation based on whether children have access to a number of household items, and income measures such as 50 per cent or 60 per cent of the median household income.

It would be up to the Government of the day to set targets against these measures.

"What I'm trying to establish is at least an expectation that no matter what your ambitions are, you at least set them and you're public about them," Ardern said.

"My targets will be different to Bill English's, but let's agree that we do it."

English said he was open to working with the Government, but it would depend on the detail of the bill.

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He said if the Government didn't have the cash to lift incomes for poorer families, then setting targets wouldn't matter.

"Setting the target doesn't deal with the practicalities.

"Because of the choices they've made and the uptake in debt and increase in spending on a whole lot of other things ... the practicalities of it are that after the Government package for April 1, they won't have any more money to do anything about lifting incomes.

"In approaching child poverty, we want to see that this isn't just a slogan."

Last week the latest data from the Child Poverty Monitor showed that 10,000 children were helped out of severe poverty, while material hardship for 20,000 children had been reduced.

Ardern said she hoped the previous Government's boost to welfare payments would see that reduction continue.

"Credit where credit's due. But I think we can do better."

New Zealand has also signed up to the United Nations' Sustainable Development Goals, pledging to halve child poverty by 2030.

The families package, which is part of the Government's 100-day plan, will include the Winter Fuel Payment, Best Start and a boost to Working for Families. It will replace the planned tax cuts of the previous Government, which was going to lift 50,000 children out of poverty.

Ardern said the families package would help children in poverty more than the previous Government's tax cuts.

"Seventy per cent of families will be better off."