Leaders from both major parties in state government, the Greens and local government were "in furious agreement" that planning needed to focus on leveraging heritage buildings to create a modern city, higher density city living and a sophisticated transport system. Planners would also need to continue the vibrant city strategy to make the Adelaide CBD a business, entertainment, residential and aesthetic centre.

Deputy Premier John Rau, Shadow Minister for Economic Development Martin Hamilton-Smith, Greens Leader Mark Parnell and the Adelaide Lord Mayor Stephen Yarwood told a CEDA election forum that South Australians could no longer afford the suburban sprawl started in the 1950s and 1960s and must focus on infill rather than greenfields housing developments.

The idea of affordable housing being on the metropolitan fringe was a myth, they said, given the significant costs of transport and infrastructure.

"The idea that we can continue to consume particularly arable farmland on the boundaries of the current metropolitan area is unsustainable," Mr Rau said.

While low income earners were lured with cheap house and land packages, they underestimated the ongoing costs of transport and taxpayers were generally lumped with the infrastructure bill over generations.

Mr Rau said successive governments had not been honest with themselves about how much these far-flung developments would cost future tax payers, because in the current electoral cycle they didn't need to worry about funding beyond the four-year forward estimates. From an economic development perspective, 1000 new dwellings in the city provided a much greater economic benefit than the same number in an outer metro area, he said.

Older retired people in particular were likely to be drawn into the city over time, the speakers said.

Adelaide Lord Mayor Stephen Yarwood said the Adelaide City Council must work with state and federal governments to build an integrated transport system and a strategic plan that provided more sophisticated linkages to the city in the evening.

But while Mr Yarwood and other speakers argued that local government should have planning powers because councils understood local planning needs better than state governments, Mr Rau said planning authority must reside in the hands of the state government to ensure quality and independence.

Mr Hamilton-Smith said that like Paris and Boston, Adelaide could blend heritage and new buildings to create an attractive street-scape.  He said that, having relocated major sporting events back into the city, planners should now focus on bringing the entertainment centre back to the city, developing the area over the railway lines near the new hospital and redeveloping the River Torrens beyond the weir.

"I would have liked to have seen something that could have been enjoyed as an open space to complement the river we already have," he said. Yet in planning, leaders must remember that they were custodians of the city of Adelaide for the whole state. "We don't own it," he said.

Leader of the Greens Mark Parnell said developments such as the new skate park were important tools to bring people back into the city - "Because we're not designing our city for oldies, we are designing it for a whole spectrum of ages and abilities," he said.

All levels of government would need to be bold and use a combination of carrots and sticks - such as the city parking levy and stamp duty concessions for city apartment developments - to create a sustainable city, Mr Parnell said.