The number of people seeking emergency accommodation and turning to Citizens Advice Bureau for help has doubled in five years.
Citizens Advice Bureau (CAB) received more than 3000 enquiries about emergency accommodation this year, up from 1500 in 2010, a recent report shows.
Overall there have been 10,000 such inquiries in the past five years.
CAB chief executive Kerry Dalton said a national shortage of emergency housing was partly to blame for the increase in the number of people asking CAB for help.
Families were sleeping in cars, garages or in overcrowded houses, and the agency was struggling to find accommodation for them.
"The situations that are the most concerning are the ones that involve children. We've seen instances where there's been a mother and four children sleeping in a car and the children are falling ill, there's parents and six children living in a van, a mother living in a car with two preschool children and a newborn baby."
In another case, a family with children was living in a small house with a total of 26 occupants.
Some government agencies failed to help those who came to them, she said.
"We're seeing people who have been to Work and Income, Housing New Zealand, the Ministry of Social Development seeking assistance.
"Sometimes they're the highest priority on the social housing register, which means that they're assessed as needing a house now but they have been referred to us without being helped into alternative accommodation while they're waiting," she said.
She was hopeful the government would step up and intervene.
"I really believe that if there's a will this can be addressed tomorrow.
"It's a matter of the Ministry of Social Development and the government committing to making sure that when people come to them...they can get alternative accommodation, because the emergency accommodation just isn't there."
Labour Party housing spokesperson Phil Twyford said the surge in numbers was a result of the government letting the housing crisis get out of control.
He said it should make more houses available and put money on the table for social service agencies. "If the government made this a priority they could fix this problem today."
Green Party co-leader Metiria Turei said the government should have an intensive programme of building new social housing that people could afford.