The State Opposition has accused Liberal Party candidates of failing to tell the public the whole story in their push for multi level car parks at Perth train stations.

The candidates for Gosnells and Joondalup have distributed election material calling for the car parks and promising to lobby the Transport Minister, Troy Buswell, on the issue.

Last July, the Department of Transport's Director General, Reece Waldock, told a parliamentary committee such a facility would cost drivers $20 a day.

Opposition Transport spokesman Ken Travers says that is unaffordable and he has called on the government to declare whether it supports the proposal.

"The Premier made a promise at the last election about building an Ellenbrook railway line, and then tried to deny it and blame it on his candidates," he said.

"So it's really important that it's clear what are the Liberal commitments coming into this election, they need to be confirmed by the Premier and they need to be outlined by the ministers."

Mr Buswell has been contacted for comment.