Treasurer Tim Pallas said on Tuesday he would not rule out using powers granted to the Treasurer under the State Owned Enterprises Act, set up by Kennett government treasurer Alan Stockdale, to sell the port if the Coalition proceeded with its threat.

"Our preference is to get this done in a co-operative way with the Parliament," Mr Pallas said. "But we are not in the business of allowing the opposition to create uncertainty and conjecture about whether or not promises will be honoured."

The Coalition could blow a $5 billion to $7 billion hole in the budget by opposing the sale of the Port of Melbourne.

Despite supporting the idea when in government, Opposition Leader Matthew Guy confirmed that the Coalition would block the sale in the lower house, and then stall it in the upper house by referring the proposal to an inquiry.

With the Greens also opposed, there is significant doubt about whether the sale could go ahead early next year as planned.

Greens leader Greg Barber confirmed the Greens were opposed to the sale, and would support referring the legislation to an upper house inquiry. That means the legislation will be blocked in the upper house while the inquiry deliberates.

The Coalition has significant concerns, Mr Guy added, particularly with a clause that would entail the government paying compensation to a port operator if another container port is developed within 70 years.

Mr Guy said the Coalition would "not vote for financial vandalism", claiming Labor's proposal was "completely unacceptable".

"Daniel Andrews' proposal to insert a 'poison pill' clause into the contract exposes Victorians to massive compensation if a second container port is developed during the lease," Mr Guy said.

Shadow treasurer Michael O'Brien said on Tuesday morning that the Coalition had factored the Port of Melbourne sale proceeds into its bottom line when it was in government. In May, Mr O'Brien accused Labor of "killing off any prospect" of a second container port for Melbourne for 50 years.

The proceeds of a sale – which could be more than $7 billion – would be used to fund the Labor government's two-term commitment to remove 50 level crossings on suburban rail lines, and other transport projects.

Also at risk is about $1 billion of federal funding from the Abbott government's asset-recycling scheme. States and territories will receive 15 per cent of any asset sale as a bonus payment from the federal government if the money goes into new infrastructure. The incentive scheme is open for another 18 months.

With the Greens against the sale, Labor needs the support of the opposition in the upper house to pass the legislation.

Mr Pallas said the Andrews government would not follow the example of Prime Minister Tony Abbott and break election promises.

He said the government was still on track to meet its own deadline of securing the sale by the first quarter of 2016, and would be prepared to look at "reasonable amendments".

Mr Pallas also rejected suggestions that no new port could be built in Victoria without compensation, saying as soon as the Melbourne port reached capacity a new one could be established.

Ramping up the rhetoric against Mr Guy and his opposition colleagues, Mr Pallas said they would need to explain to residents waiting for level-crossing removals why there could be delays.

Victorian Employers' Chamber of Commerce and Industry chief executive Mark Stone said the organisation supported the leasing of the Port of Melbourne.

"[We] hope that legislation to enable this is passed by Victorian Parliament swiftly, so this important project can be progressed for the good of Victoria's broader infrastructure needs," Mr Stone said.

Infrastructure Partnerships Australia chief executive Brendan Lyon also warned against a delay, particularly risking Victoria's access to federal funds.

"Leasing the Port of Melbourne is clearly in the state's interest, because it's the only real option to get major infrastructure funded," Mr Lyon said.

He said debate about the detail was important and valid but given bipartisan support for a port lease it expect the issues to be resolved during the Parliament's deliberations.