The Coalition outlined five reasons it is opposed to the major road project: that the government did not take the project to the last election and therefore has "no mandate;

that there was no competitive tender for the $5.5 billion project, which follows an unsolicited bid by Transurban;

that traffic modelling is "dubious", based on evidence given to the Australian Senate by transport expert William McDougall, who was contracted by the Transport Department to advise it on the business case;

that the road is of dubious benefit, given modelling indicates part of it will be in a state of peak-hour gridlock within 10 years of opening, and;

that it is unfair to impose an extra 10 to 12 years of tolls on CityLink users to pay for the road. "Our position is that we do not support the Andrews Labor government making motorists in the south-east and the north of Melbourne pay CityLInk tolls for 12 more years for a road they are not using," the letter to Transurban states. The Coalition said however that it would not tear up contracts for the West Gate Tunnel if they are signed. Transurban's "unsolicited" offer to build the West Gate Tunnel hinged upon an extension to its toll deal on CityLink in order to fund the project.

But extending tolls on CityLink requires the approval of the Victorian Parliament and the government has just 14 votes in the 40-seat upper house while the Coalition has 16. The Greens hold five votes and there are five crossbenchers. "As you are aware, the Victorian Coalition does not presently command a majority of votes in either the Legislative Assembly or the Legislative Council. We therefore cannot secure passage of a disallowance motion in our own right," the letter states. "Notwithstanding this, it is appropriate that prior to Transurban entering into any contract with the Andrews Labor government with respect to the West Gate Tunnel proposal, you are given notice as to the position of the Victorian Coalition in this matter." A Transurban spokesperson said: "It's disappointing to see the Opposition oppose a project that Melbourne desperately needs. "This project will benefit motorists, including CityLink users, who regularly battle the chaos caused across our freeway network by incidents and congestion on the West Gate Bridge."

An Andrews government spokesman said the Liberals "built nothing in four years and they now oppose the congestion-busting road projects that Victorians urgently need." The move by the Coalition has similarities to the course of events leading up to the 2014 state election. Then, a year out from the election Labor vowed to overturn the Napthine government's East West Link project, repeatedly claiming the contract to build the road was "not worth the paper it is written on". In government though, its legal plan to dump the road collapsed and it cut an expensive settlement deal to extricate the state from the project. Labor, like the Coalition on Friday, also said Dr Napthine had no mandate to build the East West Link because it had never been put before voters at an election. It also said the traffic claims made for the road did not stack up.

The government based that decision on legal advice that said it could cancel the contracts signed to build the road. Once in government, it abandoned this legal advice. Roads policy is shaping up as a flash point in the 2018 election. The Coalition has also promised to build the East West Link, which was cancelled by Labor in 2014. It has also pledged to remove 55 major intersections across the suburbs by building underpasses.