Labor's three-pronged poll push in Canning

Labor continues to run its Canning by-election campaign in tandem with its state and federal election push.

It's promising a new train station in the electorate while lashing the Liberals for not doing enough for rail.

State opposition leader Mark McGowan pledged on Tuesday that if Labor wins the 2017 state election, it will build a new train station at Karnup to ease pressure on the existing Mandurah and Warnbro stations.

The proposal is part of Labor's ambitious Metronet plan, which was the centrepiece of its 2013 election campaign.

Canning candidate Matt Keogh criticised the prime minister for refusing to fund urban rail.

He says the opposition's commitment stood in stark contrast to "what Mr Abbott is doing, which is showing up for a few photo-ops".

"The only investment he's making into the electorate of Canning is currently paying for advertising," Mr Keogh said.

It's the second Metronet promise in the past week, with the opposition also pledging a rail line at the other end of Perth in ever-growing Ellenbrook.

Premier Colin Barnett responded by saying it wouldn't be needed for up to 20 years, despite the Liberals having previously promised to build it.

Critics of the revived Metronet plan say it's just a dusted-off proposal that leaves the basis for Labor's 2017 state election campaign locked in.