Unoccupied homes in Sydney would be hit with a substantial rate increase, under a radical plan to ease the city's housing shortage.
About 10,000 homes around the CBD - or more than one in 10 - were found to be vacant on census week in 2011. (For greater Sydney, an area that extends through to the Central Coast, the figure tops 120,000).
The number truly unoccupied for long periods is likely south of that figure, but a number significant enough to make a difference, according to Wendy Hayhurst, CEO of the Federation of Housing Associations, a group representing providers of affordable housing.
"Many of these are 'city homes' for people who visit a couple of times a year, or investment properties sitting empty," she said.
While debate on affordability has so far centred on major reforms to negative gearing and land tax, the Federation wants to instigate local change.
"This is an idea that the City of Sydney can act on now. Given the scale of the affordability problem, we need to look at everything."
The FHA has asked the council to consider increasing rates for those who leave properties vacant for an as yet undefined period of time between several months and two years.
That would provide an incentive for new homes to be released onto the market, or, for those who simply wear the cost, more revenue for affordable housing projects.
Under a similar policy in the UK council of Camden, homes left vacant for two years are hit with a 50 per cent premium on their rates; a reform credited with a near-halving in the number of unoccupied properties.
It is not known how many homes in Sydney would meet the criteria and Mrs Hayhurst is calling for council to investigate reasons.
But anecdotal evidence from some real estate agents suggests some investors may leave homes vacant while chasing a short-term return.
"In the face of escalating prices where a single home can increase by $50,000 to $100,000 a year, [some investors may indeed forego] a rental return of $15,000 to avoid risk," said Philip Soos from LF Economics.
One analysis in Melbourne by think tank Prosper Australia, suggested more than 20,000 homes in that city did not use any water each year.
"The proposal [...] will be considered and the findings incorporated into a final report," a spokesman for Clover Moore said while adding that selective increases on rates were not currently allowed by law.
Chris Johnson from the Urban Taskforce, a lobby that represents the development industry, said he feared defining what constituted an 'unoccupied' property would be fraught and difficult to enforce.
But he said he would not oppose a levy on absentee owners.
"This is not about people who go on holiday, or are doing renovations and we're not talking about mum and dad investors," Mrs Hayhurst said.
The state's treasurer, Gladys Berejiklian, said the government preferred to tackle housing affordability by increasing supply.
"Under our policies, building approvals for new housing has reached its highest levels in two decades," she said.
The government committed $400 million to a housing acceleration fund in this year's budget.
