The Greens want an assurance from the Government that it won't privatise Child, Youth and Family.
They're afraid ministers will use the damning report by Commissioner for Children Russell Wills as a reason for handing over vulnerable children to private care providers.
Mr Wills said in the report, released on Thursday, that the department didn't even know whether children were better off in its care.
"Generally speaking, the longer a child spends in CYF care, the more likely they are to experience harmful consequences," he said.
Green Party MP Jan Logie says Social Development Minister Anne Tolley hasn't ruled out privatisation.
"It looks like the Government has systematically under-invested in Child, Youth and Family, just as it has with Housing New Zealand, to justify privatising these core government services," she said.
"The report into state care of our most vulnerable children should be a call to action, not a call to sell."