People living in night shelters were excluded from the research.
"Homelessness is worsening in New Zealand in terms of both numbers and as a proportion of the population," researcher Kate Amore said.
"If the homeless population were a hundred people, 70 are staying with extended family or friends in severely crowded houses, 20 are in a motel, boarding house or camping ground, and 10 are living on the street, in cars, or in other improvised dwellings."
All of these people needed urgent, affordable housing, she said.
The issue of people living in cars and garages in South Auckland came into the spotlight ahead of last week's Budget, as Government came under pressure to control the housing market.
The Government invested $41 million in emergency shelter in the Budget, along with $200 million for new social housing places.
It also re-jigged a social housing policy to offer homeless up to $5000 to relocate out of Auckland, where the housing shortage is most acute and the wait-list for state houses is the longest.
Social Housing Minister Paula Bennett was unable to respond to the findings as she was travelling.
A spokesman pointed to the various policies which were underway to address homelessness.
They included short-term grants which tenants did not need to pay back, and changes to the social housing register which placed greater priority on homeless or people in insecure housing.
As signalled last week, a "flying squad" of Ministry of Social Development (MSD) staff and NGOs tracked down homeless in Auckland this week to assist with getting them into emergency housing.
The team spoke to nearly 400 homeless people, some of whom had were now being assessed for the social housing register. Others had declined support.
Labour leader Andrew Little called for more urgent action, saying the Government's commitments fell "woefully short of what is needed".
"The funding the Government offered in last month's Budget is only enough to cover 800 places at a time and will go towards mostly existing beds," he said.