Bill Shorten has challenged Malcolm Turnbull to match or better his pledge to create a $1.6 billion fund for Western Australia to make up for a shortfall in its GST share.
The federal Labor leader on Saturday ridiculed the prime minister for claiming to be the first to acknowledge the state's current GST return was unfair.
"I plan on being the first prime minister to fix the problem," he told party faithful at WA Labor's state conference in Perth.
He said the rate of 34 cents for every dollar was a "dud deal" for the state, but Labor's promised Fair Share for WA Fund would boost commonwealth funding to the equivalent of a 70-cent floor.
The measure would be legislated to include a guarantee that all proceeds are invested into WA infrastructure projects.
"I challenge Mr Turnbull - if you think you can do better, come across and tell us how," he said.
"I can't help Western Australia until the day after the next election. He can help them on Monday."
WA Premier Mark McGowan described it as a "giant leap forward" and welcomed competition for the "affection" of West Australians.
"Mr Shorten has led the way and now I call on Malcolm Turnbull to take action," he told reporters.
But Mr McGowan conceded the funding fell well short of the $10 billion he wanted under a per capita GST system.
"I'd like to see more in time, obviously," he said.
Federal Finance Minister Mathias Cormann labelled it another unfunded Labor promise, noting former prime minister Kevin Rudd promised $100 million a year for infrastructure in 2007 but never delivered.
He said Mr Shorten wasn't proposing to fix GST sharing arrangements for WA and was simply "trying to play catch-up."
"He's trying to copy the Turnbull government's approach to GST," Senator Cormann said.
"We've been making federal top-up payments to Western Australia for the past three years to the tune of more than $1.2 billion."
WA opposition leader Mike Nathan also labelled Labor's plans a copy of the federal GST top-up payments, which was designed to be an interim solution.
"What we need is reform of GST, not higher taxation and not higher taxation and giving a little bit back. It's just a cheap trick," he said.
Mr Shorten made no secret of the fact he wants to win more seats in WA, especially those of government ministers Christian Porter and Michael Keenan.
But Labor would not rely on the mistakes, flaws or disunity of the Turnbull government.
"We will not be relying on them to trip over their own shoelaces or to open the constitution and read it," he said to laughs.
"We will offer Australia a social and economic program for the betterment of this nation and its citizens."
