The WA Government has set itself up for a pre-election fight with environmental groups opposed to the Roe 8 project, with Premier Colin Barnett saying construction on the contentious heavy-haulage route will be underway before March.

Despite repeated urging from the Opposition not to lock in the project before the election, Mr Barnett said "it will be underway" before the March poll.

Mr Barnett's comments come despite the resignation of his transport minister Dean Nalder, who said the Premier was being "irrational and illogical" by not wanting to proceed with the second stage of the Perth Freight Link project at the same time.

Roe 8 forms the first stage of the Freight Link, with a link to near Fremantle Port then proposed to follow.

Roe 8 is controversial for both economic and environmental reasons, with opponents arguing it will cause irreversible damage to the Beeliar Wetlands, and Labor argues the project should not progress before March so it is not forced to proceed with it if it wins the election.

But Mr Barnett said the Government would be pressing ahead.

"We will be signing the contracts for Roe 8 through to Stock Road well before the election and hopefully construction will be underway," he said.

"The people south of the river want to see that project and it will be underway."

During days of leadership turmoil, Mr Nalder blasted Mr Barnett's direction on the project and urged the Government to go ahead with both Roe 8 and the second stage at the same time.

Mr Nalder wanted stage two to be in the form of a tunnel, something Mr Barnett said would "most likely" happen eventually.

"The former minister was certainly keen to see it rolled into one contract, that is not realistic and it is not going to happen," Mr Barnett said.

"We are doing the project in its correct sequence.

"A lot of work needs to be done until the Government is in a position to sign a contract on that basis [for the second stage] but we intend to proceed with that."

Meanwhile, the Government has indicated Labor would be able to renege on any Roe 8 contract if it wins the election with only minimal financial penalty.

Asked in the Legislative Council what would happen if a new government after the election chose to renege on a Roe 8 construction contract, parliamentary secretary Jim Chown said costs would only be incurred for work already completed.

Asked if that cost was expected to exceed $500 million, Mr Chown said it was not.

Parallels have repeatedly been drawn between the Roe 8 situation and Victoria's East-West Link scenario, with that state ending up paying hundreds of millions of dollars to not build a road after a new Labor Government ditched the previous Liberal administration's project.