National Party leader Bill English says he won't be joining the conversation about child poverty until the Government "shows that it's serious".
"This is the difference between having the intent, which they're good at, and dealing with reality which generally they're a bit shambolic at," the opposition leader told The AM Show on Tuesday.
Jacinda Ardern wants to drop politics to get cross-party buy-in for the Government's new child poverty legislation.
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," she told The AM Show on Monday.
"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'.
"My view is we will not get a long-standing solution to issues like child poverty and like climate change, until we can get over the three-yearly political cycle."
Mr English says he accepts the plan could have the immediate effect of reducing poverty numbers by up to 60,000 - similar, he says, to National's election proposal - but says after that progress will fall flat.
"They've spent all the rest of the money on tertiary education and a whole lot of other stuff you can't quite follow.
"If they're going to have child poverty reduction targets, the Government has to show how they're actually going to achieve them. Otherwise you're just fooling people.
"There is no indication they've got a plan at all. So putting legislation targets will look a bit cynical when there's actually no plan."
But he's not ruling out backing the Government.
"We would come on board if there are some genuine plans to reduce child poverty."
A report released last week found small reductions in child poverty between 2015 and 2016, prior to the then-Government's benefit increases.
The latest Child Poverty Monitor shows 12 percent of children are living in material hardship, down from 14 percent in the previous report.