The Prime Minister has escalated his dispute with Mark McGowan over Western Australia’s hard border closure, warning the Premier his “all-or-nothing approach” will “highly likely” fall foul of the constitution.

Clive Palmer’s WA border dispute is being heard in the Federal Court this week, before heading to the High Court later this year.

Scott Morrison has defended the Commonwealth’s decision to join Mr Palmer’s action.

He said he was concerned about the “combative” way the debate had unfolded.

“I do fear an all-or-nothing approach on the case is not the best way forward because I think the constitutional position is fairly clear,” he said.

My concern is that it is highly likely that the constitutional position that is being reviewed in this case will not fall in the Western Australian Government’s favour.”

Federal Attorney-General Christian Porter insisted the Commonwealth was not “siding” with Mr Palmer.

Mr Palmer’s border challenge will be decided in the High Court later this year. Photo: AAP

“This is not about any great love or any great dislike for Clive Palmer,” he told 6PR radio.

“The problem with [the border closure] is it’s a complete all-or-nothing approach.

“If you maintain an all-or-nothing approach, then you run a very high risk that you will have the High Court determine against you in the long run, which might be October or whenever.”

McGowan not budging over ‘selfish’ Palmer

Mr Porter agreed it “made sense” for Western Australia to close its border to Victoria due to the large number of coronavirus cases in that state.

“But it is less proportional and makes less sense for WA for instance to close its borders to South Australia when each jurisdiction has … no community transmission and very low rates of active cases,” he said.

“I think that the compromise position here is to try and very cautiously, in a staged, sensible, jurisdiction-by-jurisdiction way, start to open your borders.”

But Mr McGowan said the state would continue “fighting” the case, arguing the border closure was keeping West Australians safe.

Premier Mark McGowan says Mr Palmer is a “very selfish and self-centred person”. Photo: ABC News

It annoys the hell out of me that the Liberal Party and Mr Palmer want to bring it down,” he said.

“It’s to protect us.”

Mr McGowan described Mr Palmer as “a very, very selfish and self-centred person” who was “prepared to risk everyone’s health for his own travel arrangements”.

• Related: Clive Palmer charged with fraud

‘Targeted’ border closure better: expert

The Federal Court has been hearing evidence from a panel of expert witnesses including epidemiologists Kamalini Lokuge and Tony Blakely and infectious diseases expert Peter Collignon, who said WA could consider a “targeted quarantine regime” that would apply only to travellers from interstate virus hotspots.

Dr Collignon said a travel bubble between WA and other states with no community transmission of coronavirus would have fewer economic and social consequences for the community and would be more sustainable than the current border closure.

WA’s border was closed in late March, in the early days of the COVID pandemic. Photo: ABC

The Australian National University professor also criticised Western Australia’s hotel quarantine arrangements, saying they were not as rigorous as those in NSW.

He said instances where security guards had contracted COVID-19 indicated the system was not as robust as that in place in Sydney.

“What I’ve read is WA is doing less than other states. It’s quite a worry that three of your security guards have got COVID when they shouldn’t have,” he told the court.

“If you don’t have absolute rigorous control of the highest-risk individuals, returned travellers, that’s the highest risk of leakage into your community.”

Hotel quarantine criticism rejected

WA’s chief health officer Andrew Robertson rejected Dr Collignon’s suggestion, telling the court the state’s quarantine arrangements were as good as, if not better, than those in other jurisdictions.

“The hotel quarantine arrangements, particularly for international visitors, are every bit as robust as those of NSW,” he said.

“[Travellers] are managed by a now very experienced and trained security force who are trained in PPE, and they are monitored by Department of Health staff from our hospitals.”

Earlier in the trial, Dr Robertson conceded there was little public health justification for keeping WA closed to the five other states and territories that had eliminated coronavirus.

He told the court he had written to the State Government suggesting it consider a travel bubble with SA and NT.

The Federal Court hearing is determining the facts of the case before it goes to the High Court later this year.

–ABC