The 50-year-old is wanted in the US over the publishing of thousands of secret US diplomatic and military files, some of which revealed war crimes in Iraq and Afghanistan.

Assange is also accused of trying to recruit hackers to provide WikiLeaks with classified US information, and if found guilty could face up to 175 years' imprisonment.

In the UK the High Court ruled on Friday he could be extradited to face 17 charges, after a lower court ruled Assange shouldn't be sent to the US due to a real and "oppressive" risk of suicide in January.

Senior judges ruled that risk was mitigated by assurances from US authorities that the father of two wouldn't be held in highly restrictive prison conditions.

Assange's lawyers intend to challenge the court's ruling with another appeal, this time in the UK's Supreme Court.

Federal Independent MP Andrew Wilkie is calling on Prime Minister Scott Morrison to "end this lunacy" and demand the US and UK allow Assange to be released.

"Mr Assange should be looking forward to spending Christmas with his two young boys and his fiancee, but instead he's facing a 175-year jail sentence and the very real possibility of living out his final days behind bars," he said in a statement.

"He is a hero, not a villain, and journalism is not a crime.

"Again the United Kingdom proves it's a lackey of the United States and that Australia is delighted to go along for the ride."

The Department of Foreign Affairs and Trade said it respected the UK legal process and Australia was not a party to the case.

DFAT said it was monitoring Assange's case, had offered him consular assistance and sought his consent to discuss his health situation with UK prison officials, but he hadn't responded.

The department did not comment on Mr Wilkie's call for the government to demand Assange be released.

"The Australian Government has raised the situation of Mr Assange with US and UK counterparts - including our expectations of due process, humane and fair treatment, access to proper medical and other care, and access to his legal team - and will continue to do so," a DFAT spokesperson told AAP.

The UK court's decision has drawn ire from the United Nations' special rapporteur on torture, Nils Melzer, who sharply criticised the verdict.

"This is a shortcoming for the British judiciary," Mr Melzer told the DPA news agency on Friday.

"You can think what you want about Assange but he is not in a condition to be extradited," he said, referring to a "politically motivated verdict".

Assange has been held in the UK"s Belmarsh Prison since 2019 after he was carried out of the Ecuadorian embassy by police and arrested for breaching bail.

He initially entered the building in 2012 to avoid extradition to Sweden where police wanted to interview him about sexual assault allegations, which he has always denied and which were eventually dropped.

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Australian Associated Press