The Abbott Government faces pressure to reveal key details about its contentious $1.6 billion Perth Freight Link.
The Greens and ALP will today back a motion in the Senate that would force the Government to release the cost-benefit analysis of the project.
In the Budget the Government revealed it would pump $925 million into the project which aims to link Perth Airport with Fremantle Port via the Perth Gateway, Roe Highway, Stock Road and Leach Highway and includes the controversial Roe 8 extension
The State Government, which has not set aside any money in the Budget for the project, would need to find about $230 million.
Another $450 million would come from the private sector which would be able to toll heavy vehicles on road.
The Federal Government has claimed a private cost-benefit analysis has found the freight link will deliver $5 in economic benefits for every dollar of spending.
But it has refused to release the study.
The motion that will get support in the Senate would require the public release of the study.
It also requires the Government to release all communications between the State Government and its Federal counterpart about the project.