"It's intended to look generous but when you look into it's not. It's a magic show when as many as 270,000 children need our help."
Ms Kiro said people were all for tax relief but taxation was the basis of paying for health, education, infrastructure and defence forces, to name some services.
"So what is good about a tax cut when we need those taxes to meet those costs, and more?"
The national CPAG body said the tax cuts offered nothing for beneficiary families, and the package would lift only 35,000 children out of housing poverty, fewer than half of those who were suffering hardship.
Ms Kiro said the Budget had missed the opportunity to put money, resources and a new mindset into many problems New Zealand's poor faced, particularly in Tai Tokerau.
She advocated spending money on education for primary caregivers, saying the mother's education was crucial to whanau outcomes.
Mr O'Brien spoke of the importance of universal rather than targeted change-programmes.
He criticised the Government's using the term "social investment", something he said was geared to measuring return or profit at the end of a process rather than focused on providing the means to make change earlier.
"We need to ask why would we invest in something from which there is no return."
The Treasury's analyses was based on linking risk with outcomes but, with one-third of children identified as at-risk having good outcomes in life, "we need to be very wary about that as it seems to be a bit hit-and-miss."
The Budget did nothing to deal with homelessness, he said.
Increasing accommodation supplements did not provide more or better housing but might cause rents to rise, Mr O'Brien said.