The coalition will take a new GST deal to the next election if Labor blocks proposed changes because they don't guarantee all states are better off.
Opposition Leader Bill Shorten originally said he was on a unity ticket on a GST floor for Western Australia in August.
But after seeing the proposal, Labor is concerned there is no protection in the draft legislation to guarantee a better deal for all states.
Prime Minister Scott Morrison is adamant the overall package will leave all states and territories better off, challenging Mr Shorten to support the bill in parliament.
"The crab walk seems to be starting from him when it comes to the fairer deal on the GST that WA deserves," Mr Morrison told reporters in Perth on Tuesday.
The package guarantees WA's GST share stays above 75 cents in the dollar, after to crashed to below 30 cents following the mining boom.
While eastern states have raised concerns they'll be worse off under the deal, Mr Morrison says he doesn't need their approval to pass the legislation.
"The only person who can derail the better fairer deal for WA is Bill Shorten," the prime minister said.
He vowed to take the package to the next election if Labor abandoned support for the measures.
Mr Shorten said WA had been unfairly treated, but he wanted to make sure no state would be worse off.
"Let's not play any silly games here," he told reporters in Melbourne.
"I don't want to see Tasmania, Queensland, any of the other states, Northern Territory disadvantaged because the government's trying to chase a few votes in Western Australia."
Treasurer Josh Frydenberg said the coalition government had made changes to online sales and compliance, which means an extra $6.5 billion was now being caught in the GST net.
He said the government can pay for changes to the GST because the coalition was bringing the budget back to surplus.
"The Labor party talking about budget surpluses is like Hugh Hefner talking about abstinence, it just doesn't make sense," the treasurer said.
Shadow treasurer Chris Bowen says Labor will seek answers about why a guarantee has been left out of the proposed bill.
Legislation is expected to be introduced when parliament reconvenes in a fortnight.
State and territory finance ministers will also discuss the draft laws when they meet in Melbourne on Wednesday.
