Australians could be heading back to the polls sooner, rather than later, if the August 21 election produces a hung parliament, an academic says.

Politics Professor Clem Macintyre, from the University of Adelaide, says negotiating with up to four independents would be challenging for any government.

"The whole situation becomes very unstable and you'd probably be expecting it to not last all that long," he told ABC Radio on Friday.

"There'd be every chance that we'd be going back to the polls fairly soon."

Most opinion polls point to a close result, prompting speculation of a hung parliament, with Labor falling short of the numbers it needs to rule in its own right.