CityLink toll road operator Transurban paid no company tax to the Australian government for three years despite revenues of nearly $6 billion.

As the Victorian Liberals turned up the political heat on Transurban on Wednesday the company defended its tax record, saying it complied with the law and had contributed more than $1.1 billion “at investor level” to Commonwealth coffers since 2002, through taxes on dividends paid to shareholders.

The Liberals vowed on Wednesday to "follow the money", if they win power in November’s state election, with a full audit of the hundreds of millions of dollars paid by Melbourne motorists each year to drive on the CityLink toll road.

Drivers who pay to use the road deserved to know where their money is going, Shadow Treasurer Michael O'Brien said, accusing the Andrews government of handing over billions of dollars of "free money" to the roads operator through the new West Gate Tunnel deal.