Melb toll road details release promised

The business case for a Melbourne toll road proposal will be released before a final deal is signed, Treasurer Tim Pallas says.

The Age reported the business case for the Transurban proposal for the $5.5 billion Western Distributor won't be released until the government enters final negotiations to build the road.

"We will put business cases and all other relevant material in the public domain. We promised Victorians we'd be different," Mr Pallas told 3AW.

The Western Distributor proposal would connect the West Gate Freeway with CityLink in Melbourne's north.

The government wants to shift $1.5 billion of federal money meant for the dumped East West Link project to the new road.

Transurban wants to extend the tolls on Citylink to help pay for the project.

The state government was going through the "tyre-kicking" phase of the proposal to make sure it was a good deal for Victoria, Mr Pallas said.

"If it doesn't stack up we won't proceed with it," he said.

Shadow treasurer Michael O'Brien said Labor was hiding documents from Victorians after criticising the previous government's handling of the East West Link contracts.

"This is grossly hypocritical," he told AAP.

Mr Pallas also revealed Transurban spoke to Labor in opposition about possible plans for a new toll road to replace the party's smaller West Gate Distributor project.

"I knew that they came to us and that they said `we like the West Gate Distributor, but we'd like to do more'," Mr Pallas said.

"Over and above and beyond that, we saw nothing until after the election."

Mr O'Brien said this showed Labor had lied about its major road election commitment, given it knew Transurban would announce a proposal to replace.