The Christchurch City Mission says the city's housing shortage has resulted in a spike in homeless people, most of whom have mental health problems.
And it says not enough is being done to help them transition from homelessness to housing.
Christchurch City Missioner Michael Gorman says the number of people coming to the City Mission has easily doubled in recent times.
Mr Gorman says about one person a day knocks on the door looking for help finding accommodation, and most have mental health problems.
He says more housing needs to be made available, and more emphasis should be put on helping people transition out of homelessness.
Mr Gorman says homeless people - especially those with mental disabilities - struggle to enter the housing market on their own.
