The Greens have called for a developer tax in the South Australian budget to fund the construction of 4000 public homes and help ease the state's housing crisis.
Upper house MP Robert Simms says the government could raise up to $1.7 billion over four years with a 75 per cent tax on the increase in value when land is rezoned for development.
Under current rules, developers can make windfall profits but don't pay anything for the privilege, he says.
"The new government has an opportunity to significantly increase its investment in public housing by finally ensuring developers pay their fair share of tax," Mr Simms said on Friday.
"A tax like this has worked for years in the ACT. It could be introduced here in South Australia.
"It's morally wrong that we have desperate people sleeping on the street this winter, while big developers continue to make huge profits."
The Greens say Adelaide is the second least affordable city in Australia for renters with vacancy rates dipping to 0.2 per cent.
They say 30,000 people in SA are also waiting for social housing.
The state government will hand down its budget next week.
