The Opposition Leader Mark McGowan has promised to build a rail line to Ellenbrook by the end of 2018 if Labor wins the March election.
The 21 kilometre line would connect to the Midland line and stop at Morley, Noranda, Bennett Springs and Whiteman.
Mr McGowan says it would cost $863 million, excluding the cost of new rail cars.
Both major parties committed to an Ellenbrook line at the last election and Labor has constantly attacked the Premier Colin Barnett for dumping the plan.
The Premier has previously argued there is not enough demand for the line but Mr McGowan insists it is needed to cope with rapid population growth in the north-eastern suburbs.
He says the Government should never have scrapped it.
"Today, I'm here to right a wrong, the wrong that was committed to the people of Ellenbrook by Colin Barnett," he said.
"[Ellenbrook is] full of people moving in, full of people who need public transport to fix the congestion crisis."
Mr Barnett maintains the business case still does not stack up.
"Eventually a rail line will go out there as the population develops but at this stage that rail line is not justified," he said.
"Look, Mark McGowan and the Labor Party are announcing a new railway every day.
"I mean when's it going to stop?"
Mr Barnett says the Government has allocated $20 million towards improving Gnangara Road.
The Ellenbrook line is part of Labor's heavy rail proposal, known as Metronet.
Yesterday, Mr McGowan also promised to build a railway line to the Perth Airport by mid-2018.
The 10.5 kilometre rail line, stopping at Redcliffe, the airport and Forrestfield, would cost $731 million, but that does not include the cost of new rail cars to service the line.
Mr McGowan says the airport line is a priority for Labor.
Labor has costed Metronet at $3.8 billion but the Treasurer, Troy Buswell, has previously estimated it at $6.4 billion.