Your personal information could be accessed by hackers and stalkers after a massive privacy breach by the government exposed the travel data of millions of Victorians, the state's information watchdog has found.

Despite the extraordinary violation, Public Transport Victoria (PTV) and the Department of Premier and Cabinet, which released the information, are refusing to admit that commuters' personal information has been compromised.

Published myki card data allowed users to identify the travel history of themselves and others. Credit:Steve Lightfoot

In May last year, PTV gave a hacking and data science conference unfettered access to travel data stored on about 15 million myki cards used in the three years to June 2018.

The 1.8 billion "touch on" and "touch off" events on the cards included information about a commuter's route and stop number and the specific train they were on.