The Government is facing questions over migration rules that will cut New Zealand's intake of migrants' family members from 5500 to 2000 a year.
Its rationale for the cutback is that migrants' relatives are costing the country millions of dollars a year in healthcare and benefits. However, there are no recent figures to back this up.
Immigration Minister Michael Woodhouse told TV3's The Nation the changes were based on four-year-old information.
"When the parent category was last reviewed, what we did see was that the healthcare costs by them were about three times higher than in, for example, the skilled migrants," he said.
"We also saw that there were very high levels of income support both two years, and five years after they came here."
Mr Woodhouse says an impending review will determine the exact costs parents of migrants are placing on taxpayers.
"This is a very normal review that we do from time to time. No one’s taking a swipe at anybody. There are limits to the way in which we can control the residents, particularly because of our humanitarian obligations, and those family and partnerships," he said.
Greens co-leader James Shaw says the Government is " barking up the wrong tree" by putting the pressure on the family category.
"There’s huge numbers of students that are coming into New Zealand on temporary work visas and that’s actually where a lot of the pressure is coming from, especially on housing and on transport infrastructure," he told The Nation.