This was the logical way of accommodating the estimated Australian population of 35 million people by 2050.

Economist and futurist Brian Haratsis also advocates a wider ACT boundary to exploit Canberra's infrastructure so it can handle a population of one million people.

He expects Australia to break the mentality of continuing to expand established cities to handle population growth as the nation expands.

Developing a Sydney-Canberra corridor economy would meet multiple objectives including high-speed rail, a health hub to cope with a tripling of hospital beds across the nation and a second Sydney airport.

''You would connect a new major hospital around Bowral, seriously look at a second airport, whether it is Canberra or another airport between Sydney and Canberra.

''The planning for it would be now and it would happen between 2025 and 2050 because Sydney Airport gets to capacity around 2025 on BITRE [Bureau of Infrastructure Transport and Regional Economics] aviation forecasts.''

Mr Haratsis, founder and chief executive of national strategic consultancy MacroPlan Australia, said high-speed rail was caught in a hiatus of how the nation's future structure would develop. ''If it is an obscenity to double the size of Sydney, which I think it will be, then you have to say if we are to change, we have to build infrastructure.''

For more on this story, see today's Canberra Times.