The Federal Coalition's leadership instability has sparked renewed concerns about whether Western Australia will get the GST changes it has spent years calling for, with Treasurer Scott Morrison saying a Peter Dutton proposal could scuttle the deal.

Mr Morrison's warning follows Mr Dutton's proposal to remove the GST from power bills, amid the prospect of the former home affairs minister launching another challenge against Prime Minister Malcolm Turnbull.

Mr Morrison said that plan, which he referred to as a "budget blower", could have significant implications for the proposed overhaul of the GST carve-up which was designed in part to end years of complaints from WA about its low share of revenue.

"You can make all sorts of promises about how much money you'd have to spend, but at the end of the day you have got to account for it," Mr Morrison said.

The Turnbull Government promised to add extra federal funds to the GST revenue pool to boost each state's share, changes it has been hoping to get the states to agree to next month.

WA will now write to Mr Morrison as it seeks reassurances from the Coalition that the carve-up changes will proceed, regardless of whether Mr Turnbull remains as Prime Minister or is replaced.

WA Premier Mark McGowan, who described the ongoing Liberal Party leadership turmoil as "turning Australia into a laughing stock", said he was "really, really concerned" about what would happen to the GST deal.

"I am sending a message to the Federal Government," Mr McGowan said.

"Send us a letter today confirming the arrangements so we can put it into our budget, do that now, lock it in stone."

The proposed GST changes would boost WA's revenue share by $4.7 billion over eight years.

Earlier, Attorney-General Christian Porter refused to guarantee the deal would proceed if there was a change in Prime Minister.

"He [Malcolm Turnbull] is the person who fixed the GST for us with a lot of effort from myself, Mathias [Cormann] and Julie [Bishop] but everyone would need to be conscious about the fact that he is the person who fixed that for Western Australia," Mr Porter told ABC Radio Perth.

But WA Liberal leader Mike Nahan said he expected the Coalition would continue to back the proposed changes, regardless of who is leading it.

"They have put together a really comprehensive proposal, it was driven by Mathias Cormann and all the Liberals in Western Australia and I'm confident it would hold," Dr Nahan said.

"It has broad-based support from members in Western Australia and I'm sure that our West Australians would convince — if there were to be a change — to keep that."