Labour and the Greens are urging the Government to accept a challenge set by Children's Commissioner Andrew Becroft and cut child poverty by 10 percent by the end of next year.
Prime Minister John Key won't commit to a figure.
He says there are various ways to measure poverty and it's better to focus on the factors that contribute to deprivation.
The Government and Opposition parties have never agreed on a formula to work out how many families or children live in poverty.
Labour leader Andrew Little says his party accepts the challenge, thrown out by the Children's Commissioner at the weekend during a television interview.
"The debate is bedevilled by cross-talking and no agreement," Judge Becroft said.
"I think the measure should be the material deprivation rate.
There are 17 criteria and if children are in families with more than six of those they're said to be materially deprived - that's 149,000, I'd like to see a five percent to 10 percent reduction by the end of next year."
Judge Becroft wants cross-party agreement, and says Labour and National could agree to a target before next year's election.
Mr Little uses the figure of 295,000 children living below the poverty line with 149,000 in material deprivation.
"The level of child poverty in New Zealand is shocking and inexcusable," he said on Monday.
"Eight years on, Key is reduced to arguing against child poverty measures rather than just getting on with helping children in need."
Green Party co-leader Metiria Turei says the Government should "stop playing politics" and commit to a reduction target.
"The reality is that if the Government finally agrees on an official child poverty definition and a target to reduce it by, the onus will then be on National to actually do something about it - and I don't think they want a bar of that," she said.