The Victorian government has been accused of secrecy over Transurban's $5.5 billion Western Distributor proposal.
Federal Assistant Infrastructure Minister Jamie Briggs says key details are being kept from the Abbott government.
"I am stunned by the fact the Victorian government has refused to allow Transurban to provide the Australian government with any detail of the project," he said in a Committee for Economic Development of Australia speech.
"They want $1.5 billion from us but they don't want the project detail to be provided to us."
Mr Briggs also said he had met Transurban officials and was encouraged by plans for the new tollway linking the West Gate Freeway to CityLink.
The Abbott government could provide funding, he said, only if Infrastructure Australia determined the project was as beneficial as the western section of the dumped East West Link.
Victoria must also make a contribution and the tolls on unrelated roads should not be increased to pay for it, Mr Briggs said.
An official speaking on behalf of Victorian Treasurer Tim Pallas rejected the secrecy claim as "sandpit politics", saying the prime minister and the treasurer's office had been briefed and more information had been offered.
"The junior minister is simply wrong," the official told Fairfax.