Researchers from the University of Otago say 34,000 people - or about one in 120 - in New Zealand did not have their own housing in 2006 - the most recent Census and emergency housing data available.
The study provides the first statistics on the problem. It was funded by Statistics New Zealand and Housing New Zealand.
The researchers say the study worked with a definition of homelessness that includes more than those sleeping on the street, a population they say very little is known about.
One researcher, Kate Amore, says the 34,000 people were severely crowded-in with family or friends, staying in boarding houses, camping grounds, emergency accommodation, in cars or on the street.
Dr Amore says they all had low incomes. Many are excluded from poverty and unemployment statistics and are not on social housing waiting lists.
She says a quarter were under 15 years. About a third of the adults were working but still did not have housing.
Dr Amore believes the number will be larger now than it was in 2006, when the data was gathered
Situation desperate - missioner
Auckland city missioner Diane Robertson says there is no doubt a housing crisis exists.
She says the poor are being squeezed out of housing and it is probably New Zealand's biggest social issue.
"Certainly the options for the clients we work with have become less and less. We see families living together to cut down their costs - the costs of rent and associated costs - so we see I guess a lot of desperation around housing."