Adrian Whale, chairman of the trust, said his office has fielded 458 phone enquiries and conducted 289 face-to-face assessments so far this year.
Last year, the trust held 172 face-to-face assessments and 115 in 2015.
"We are turning away three times the number of families we can house, which is 16, and we estimate between 30 and 40 more state houses are needed in Whangarei immediately," he said.
The Salvation Army report said Northland's demand for social housing was partly related to relatively high proportions of the population receiving pensions and benefits, as well as the high rents relative to incomes.
Salvation Army said the number of over 65-year olds would increase in the next 15 years and, together with falling home ownership rates, the number of senior citizens in
Northland requiring social housing or income support to pay rents was likely to increase.
The median weekly household income in Northland is $804 and rent unaffordability is second behind only Auckland.
Of the 31,417 people who received superannuation in March, 8300 aged over 65 were in rental accommodation, the report said.
There were 7700 adults who received a health or disability-related benefits and together with 1800 people over 65 who are in need for social housing, the total at-risk population is 9500. The total state housing stock in Northland is only 2500.
Habitat for Humanity Northland general manager Carina Dickson said many children in Northland were living in unhealthy and unsafe houses, which must be addressed.
The state of rentals available needed to be improved, she said.
"For the first time last year, we had five applications for our Home Ownership Programme from people with no fixed address, who were camping or living in their car.
"We have also seen an increase in inquiries from people who have had the tenancy of their long-term rental ended as the property is being sold and they are struggling to find a new rental property due to the lack of supply and unaffordable rent.
"We anticipate this situation will only continue to worsen unless the supply of decent, affordable housing is increased," Ms Dickson said.