Victorians paid more than $2.6 billion last financial year in subsidies to the state's public transport operators, less than a quarter of which made its way back into the public purse through fares.

And the multibillion-dollar bill to taxpayers - already more than $10 billion - is forecast to grow in coming years, defying the predictions of those who spearheaded the system's privatisation 15 years ago.

Multibillion-dollar bill to taxpayers is expected to grow in coming years. Credit:Craig Abraham

Victoria's public transport system was privatised in 1999. Then premier Jeff Kennett predicted at the time that subsidies would steadily fall to the extent that public transport would eventually generate revenue for the state - $18.5 million a year ($28.05 million in 2013 dollars) by 2013-14, he said.

In 2012-13, state government authority Public Transport Victoria made more than $1.2 billion in service payments to private operators Metro Trains and Yarra Trams, $935 million to bus companies and $49 million to Asset Co, which manages Southern Cross Station. It also paid $361 million to regional rail and coach operator V/Line, which is a government-owned corporation.