The Melbourne to Geelong train trip would be cut from an hour to 35 minutes and a new "fast line" would link the CBD with the airport, under an ambitious 25-year plan calling for major investment in Victoria's regional rail system.

The "Intercity" report calls for the introduction of new regional trains able to travel at 200 kilometres per hour, and rail upgrades that would allow this high-speed operation "where achievable".

A revamped regional rail network would help ease the burden on Melbourne from its massive population growth, by encouraging more Victorians to live in regional cities, it says.

The plan, prepared by the Rail Futures Institute and to be launched on Monday by former deputy prime minister Tim Fischer, says a better regional rail network would allow thousands more country residents to commute to Melbourne for work, while enabling more Melburnians to travel to jobs in regional cities. It says Victoria should aim for a regional population of at least three million by mid-century.