Planning Institute of Australia police officer Audrey Marsh told the Inquiry into Regional Australia on Thursday that regional cities could, with time, get pulled in and be indistinguishable from Sydney, Melbourne and South East Queensland.

"We are potentially sleepwalking to a nation of three megacities," she said.

"If you don't want that to happen, then we need you to create a planning environment in which it does not and provide the infrastructure that allows it to maintain its individual nature."

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The Planning Institute of Australia has recommended the federal government use the newly-created National Cabinet to strengthen what was described as a "mismatch" of planning in regional areas compared to cities.

Ms Marsh said there needed to be a "national vision for how we want Australia to grow" and an investigation into the reasons for population change.

"While most of our capital cities struggle with congestion and population growth, the converse is true in many regional communities where declining populations and economic growth threatened their long-term future," she said.

"There is merit in them maintaining unique identity, a unique job market and a unique housing market - we need to create a planning system and a set of planning parameters that achieve that vision."

Committee chair Tony Pasin said travel restrictions imposed due to coronavirus meant the inquiry would be extended into 2021.

"We're looking forward to the opportunity to further connect with people who live in the regions and to develop our understanding of the challenges and opportunities found across regional communities," he said.

"This extension allows us to further examine how the Black Summer bushfires and COVID-19 have impacted regional areas.

"We hope to learn more about what our regions need in order to encourage growth, decentralisation and sustainability."