The prime minister has challenged newly elected West Australian Premier Mark McGowan to convince his fellow Labor leaders in other states to change the GST carve-up.
At the WA Liberal party's state conference in August, Malcolm Turnbull promised to introduce a floor to the GST below which no state or territory's share could fall.
But all he seems to have done since then is indicate WA will have to wait until 2019/20 for the change, which will only come after the state's share rebounds above 70 cents in the dollar under the current formula.
Mr Turnbull told reporters in Canberra on Monday that the fiercest opponents to the proposal were federal opposition leader Bill Shorten and Labor leaders in South Australia, Victoria and Queensland.
"So the challenge for the new Labor premier of Western Australia is how is he going to get his own party on side?" Mr Turnbull said.
"Labor is absolutely rock solid at the federal level, so far anyway, in defending the existing arrangements on the GST distribution.
"I believe there is an opportunity to set a floor but to do so at a time when nobody is actually going to lose."
Former state treasurer Mike Nahan, who is expected to become leader of the WA Liberals at a party meeting on Tuesday, agreed it was up to Mr McGowan to convince Mr Shorten.
He offered to work with the new premier, saying WA's Labor and Liberal party had previously achieved a change to the GST distribution, related to the treatment of iron ore fines, by working in a bipartisan way.
"McGowan has taken this, Shorten has taken this in a purely political manner, trying to wedge the GST as an attack on the Abbott-Turnbull government," Dr Nahan told ABC radio.
"I'm offering my hand to Mark McGowan to say 'let's work on this together, let's put a solution together and go to Canberra. I'll do the Liberal side, you get Shorten on side'.
"And if that works, we as a state are better."
WA's new Treasurer Ben Wyatt said Mr Turnbull had a responsibility to deliver on his August pledge.
"It's something we look forward to working with him (on) and we look forward to understand exactly when he intends to introduce a floor," Mr Wyatt told reporters before heading into Labor's first cabinet meeting.
