Prime Minister John Key is defending the government's record on housing vulnerable New Zealanders, saying it is doing the best that it can.
In the year to June, the Citizens Advice Bureau (CAB) received 3000 enquiries from people seeking emergency housing - double the number it was getting five years ago.
The bureau has called on the government to do more to ensure there is a safety net for those in desperate need of housing.
CAB chief executive Kerry Dalton said vulnerable families in need of emergency housing faced big delays.
"There's people who have gone to get help with social housing, or are on the Social Housing Register, and they have to wait for that - and, in the meantime, they're sent away and they're often left in a situation where they don't have a roof over their head," she said.
"We've seen people living in cars, having applied for social housing six months ago, with children."
Green Party co-leader Metiria Turei said the spike in desperate New Zealanders needing homes reflected a failure of government policy.
"Social agencies like Citizens Advice Bureau, like Salvation Army, have all had to take on the burden from government failure," she said.
"The only solution to this is government needs to have a very intensive programme of building new state houses, social houses, that's affordable for New Zealand families."
Labour housing spokesperson Phil Twyford said the government had let the housing crisis get out of control. But there was an easy fix, he said.
"It's simply about making a priority of making available the houses to house people, and putting some money on the table for social service agencies to help homeless people get their lives back on track," Mr Twyford said.
"If the government made this a priority, they could fix this problem today."
But Mr Key said the government was doing the best it possibly could.
"But one of the problems you've had, actually, is there's been a log jam in terms of being able to provide that support for the very low income New Zealanders, because the incentives have been for no one to move out of a Housing New Zealand property," he said.
"And it hasn't been possible to build enough houses for that increased demand."
The government was pushing for people paying market rents to move on, to free up state houses, and it was estimated about 5000 tenants were in this position, he said.
It was also trying to ensure that small families weren't living in large state homes, and that another priority was more social housing provided by community organisations, Mr Key added.
"And I think New Zealanders are starting to understand why we are doing that, because there are genuinely people who are living in conditions which are just not acceptable.
"We need to find a way through that, but the only way through that is more supply," Mr Key said.
Social Housing Minister Paula Bennett's office said 81 households on the Social Housing Register were placed in social housing last week.