Victorians can have no confidence the proposed multibillion-dollar tunnel connecting the Eastern Freeway to CityLink is the most effective and economical option for managing congestion, according to a blistering new Auditor-General's report.

It said not enough consideration was given to how much new projects ''increased congestion by inducing extra road use'' or whether strategies to encourage fewer people to drive were better value for money.

Possible solutions to Melbourne's congestion.

The report said pressure on state finances and uncertainty around Commonwealth contributions meant Victoria had to be smarter in how it tackled Melbourne's growing congestion with greater emphasis on managing demand.

The report said current strategies remained heavily weighted towards increasing road space ''with little attention to demand management''.