Opposition leader Bill Shorten has promised $700 million for a Perth train line if Labor wins the next federal election, but has continued to dodge questions about a long-term fix to the GST revenue carve-up.
Funding for the Morley-Ellenbrook line is part of a $1.6 billion fund Mr Shorten previously announced as a top-up for WA's low share of GST.
It is part of the WA government's $2.5 billion Metronet project, which will significantly expand Perth's rail network, and runs through the marginal seat held by Social Services minister Christian Porter.
Premier Mark McGowan called on Prime Minister Malcolm Turnbull to either match or better Labor's commitment, but said he obviously still wanted a long-term fix to the GST system.
The federal government previously agreed to reallocate $1.2 billion from the abandoned Perth Freight Link to Metronet, plus other transport projects.
Mr Shorten on Friday reiterated he would wait for the Productivity Commission's report on the GST.
"We don't believe that the only solution to pay WA more is to take funding from other states, that's why we've set up our WA Fair Share Fund," he told reporters.
Mr Shorten took a swipe at Mr Turnbull for not visiting WA often, saying he hid in his Sydney bunker.
"You can see the finger nail marks on the Nullarbor whenever he's dragged to be here," he said.
"You know he doesn't like coming here because he hasn't got an answer."
Urban Infrastructure minister Paul Fletcher said federal Labor had "no substance behind the (infrastructure) commitment and no real money to back it up".
Deputy opposition leader Liza Harvey said she supported Mr Porter but it was "irrelevant" whether she backed the Morley-Ellenbrook line, which was first promised by the Barnett government in 2008.
WA opposition leader Mike Nahan has said parts of Metronet should be scrapped because of the state's budget woes, which included a $392 million hole after a gold royalties hike was blocked in parliament.
But transport minister Rita Saffioti insists Metronet will not be derailed.
The Morley-Ellenbrook route and station locations are being finalised, plus consideration to land sales.
Additional state funding will be allocated after the business case is developed.
Construction is expected to begin in 2019 and be completed by 2022.
