It remains unknown if the WA Government will incorporate the dualling of the Bussell Highway into the Bunbury Outer Ring Road project.
The Deputy PM Michael McCormack said the WA Government were yet to formally request from the Australian Government whether they could use part of the funding allocated for the BORR to dual the highway.
However, Transport Minister Rita Saffioti said she was waiting for approval from the Federal Government to incorporate the dualling into the BORR project.
The Deputy PM said the state government announced in May and June this year that it would see if dualling the highway between Busselton and Capel could be accommodated within the cost of Stages 2 and 3 of the BORR project.
The Deputy PM said to date, the WA Government has not formally written to the Australian Government seeking to include the duplication within the scope of the project.
"The Australian Government has not yet received formal advice from the WA Government as to what savings may be available from the Bunbury Outer Ring Road project, nor the estimated final cost of the proposed Bussell Highway duplication," he said.
The Australian Government is providing $682 million towards the $852 million Bunbury Outer Ring Road - Stages 2 and 3.
The WA Government is currently preparing the Stage 4 business case which it will submit to Infrastructure Australia for assessment.
Transport Minister Rita Saffioti said following years of inaction by the former government, the McGowan Government committed $4 million to begin preloading for Stage 1 of the Bussell Highway duplication from Capel to Hutton Road, which will begin later this year.
"Stage 1 construction work is due to begin in late 2020, but to get this part of the project off the ground we need federal government approval," she said.
"To say that we are yet to seek approval from the Federal Government is incorrect - over the past five months, Main Roads has been working with the relevant Commonwealth agency to include this project in the scope of works."
Vasse MLA Libby Mettam said there was no reason why the full duplication of gighway could not be delivered by the McGowan Government as part of the BORR project, given $680 million in federal funding has been committed.
"It is extraordinary that several months after making the commitment as part of the State Budget, that Ms Saffioti has not written to Mr McCormack seeking support for the dualling of the highway. It is disappointing McGowan Labor Government currently has the funds and the means to invest in dualling the highway and is choosing not to do so."
