Western Australia could cause major problems for the Commonwealth if its Liberal Premier Colin Barnett goes through with a threat of so-called "disengagement" over his state's GST shortfall, according one of Australia's most respected constitutional experts.

With premiers due to meet in Canberra on Friday for another COAG meeting, Mr Barnett has flagged a policy of "disengagement" which. although unspecified, could result in a level of functional separation between WA and the eastern states.

And it could also see the state's assistance across a vast array of regulatory functions, currently managed under the guise of "cooperative federalism", withdrawn with major impacts for other states.

Catholic University of Australia vice-chancellor Greg Craven said while the prospect of actual secession by WA was unrealistic, it would be "foolish" to underestimate the determination in the west to get recognition that the state is severely disadvantaged by the Commonwealth Grants Commission's formula for allocation of the GST pie.

That formula would see it get back just 30 cents in each dollar of GST collected there, well below any other state. The argument saw a meeting of Commonwealth and state treasurers break up last Friday without agreement.

"It is dangerous to just dismiss this as just West Australian whingeing because often they have a point, and the second point is that people shouldn't underestimate the depth of the feeling - it's a different thing to saying legally you can't secede because this could be real problem anyway," Professor Craven said.

And WA federal Liberals agree, with Tangney MP Dennis Jensen telling Fairfax Media the anger from voters in his electorate was widespread.

Dr Jensen said he and other WA Liberals had made their position clear and were confident that Treasurer Joe Hockey understood the situation.

"I think it's been a slow trickle but now it's getting major attention," Dr Jensen said. "Let's see what happens on Friday."

The argument looks like dominating the COAG meeting with all other states equally determined that if the collapse in royalty revenue for WA from the fall in iron ore prices is to be made up by Canberra, it must not come from their GST share.

Victorian Premier Daniel Andrews said he had no sympathy for Mr Barnett's position, claiming WA had been digging money out of the ground for years.

"Mr Barnett can do all his Boston Tea Party speeches he likes but we are not having a situation where Victorians pay for schools and hospitals in Perth while Tony Abbott cuts the funding, the very funding that we need to provide better standards of care in hospitals and better standards of learning in our schools," Mr Andrews said.

Economists queried what Mr Barnett could have meant by his threat that WA may "disengage" from the rest of Australia.

Bank of America Merrill Lynch chief economist Saul Eslake said Mr Barnett has already refused to countenance lowering the GST threshold for online overseas purchases until it got what it wanted out of the GST revenue-raising formula, so he may do similar things.

"Presumably WA could obstruct any kind of intergovernmental agreement that requires the consent of all states and territories to proceed," Mr Eslake said.

"But it's hard to know exactly what he means."

Chris Richardson, Deloitte Access Economics director, said despite Mr Barnett's strange threat, his point about the need for reform at the Commonwealth Grants Commission was a good one.

"The calculations of the commission may be highly detailed but they often produce highly detailed humbug," he said.

"Australia can, and should, do better about the way it allocates money to the states but that shouldn't be a one-off fix, it needs a wider and more careful conversation."

The argument over the distribution of the GST comes as voters appeared to warm to another idea: lifting its rate. A Fairfax-Ipsos poll showed 37 per cent of voters now think the rate should be lifted to increase its overall take - and that was without either side of politics backing the idea.

There is also support of 43 per cent for winding back generous superannuation tax concessions for middle and high income earners.

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