An expert’s report says the private sector could build a high-speed rail service between Brisbane, Sydney and Melbourne for around a third of the previously estimated cost, and get it done in about a fifth of the time.

Peter Knight, a high-speed rail expert, former BHP manager and Reserve Bank economist, lays out the idea in a new book - High Speed Rail for Australia Now.

He says a network could be built for $30 billion and in less than seven years – much less than the $114 billion and 30 to 35 years estimated in government feasibility studies.

The secret, according to Mr Knight, would be to lay tracks in trenches rather than tunnels near the cities, allowing housing to be built over new inner-city land created by the trenches.

Former Deputy Prime Minister Tim Fischer said it is “a comprehensive and yet clear-cut template for getting High Speed Rail jolted into action”.

The book says the project would be best accomplished by a private consortium, and that a VFT 2 Consortium project would require little or no direct government funding.

But Mr Knight says a government guarantee of private finance would enable the project to proceed. The government money would be a contingent liability, he added, not an increase in government debt.

The benefits could be profound, with the project able to aid budget recovery, create non-mining investment, thousands of jobs and economic stimulus.

A high-speed rail network would mean fewer people have to live in major cities, boosting the populations of regional cities within 30-60 minutes commuting time of the CBD (at a speed of around 350 km/h).

The plan to build low-density housing over 30km of 100m wide trenches into and out of Brisbane, Sydney and Melbourne, would create 21 square km of new inner-city land.

Most importantly, the book argues, high-speed rail would fix distortions in the way freight moves in Australia. Mr Knight says that what should be carried cheaper by sea is currently carried by rail, and what should be carried by rail is carried by road.

Fixing these freight distortions would increase domestic productivity substantially, the analysis found, allowing Australia to become more internationally competitive and achieve greater GDP growth.