Ms MacTiernan said the Department of Transport was researching the possibility of an underground railway line from the CBD to Morley
She said the project had been costed at about $2.8 billion, but more investigation was required.
Ms MacTiernan said underground rail was the way to go.
�I think this should be made public before the election so that we can have a mature discussion about this project,� she said.
�This would be really important in terms of expenditure which should be discussed in a mature fashion.�
Ms MacTiernan said the density in the area demanded the underground rail.
�Perth is on its way to becoming the congestion capital of Australia,� she said.
�We need to look at tunnelling, the price has been driven down; boring machines are cheaper now.�
She said it was a better option than light rail or buses.
�Light rail is important but it is not adequate for moving the number of people in that area,� she said.
�Light rail is more for shorter trips; usually you would get off the train and use light rail to get closer to your destination.
�There is a place for buses in Perth but again they are not able to move the large number of people.�
A Department of Transport spokeswoman remained tight lipped when approached for confirmation of details.
�The strategic context for all future rail lines in metropolitan Perth is being further considered as part of long-term planning investigations for the Perth Transport Plan for 3.5 million people and beyond,� she said.
�Planning and Transport Research Centre (PATREC) is conducting a study as part of the plan. No current timeframes or funding exists.�