Mr Assange remains in London's Belmarsh prison pending a High Court appeal to block his extradition to America to face charges after exposing war crimes.

His brother Gabriel Shipton and father John Shipton were at Parliament House in Canberra on Thursday, where more than two dozen MPs, senators and representatives were briefed on Mr Assange's ongoing legal situation.

While Prime Minister Anthony Albanese has previously stated "enough is enough" regarding Mr Assange's ongoing detention, Gabriel Shipton questioned why efforts to secure his release could not be publicly disclosed.

He again outlined his brother's precarious health position after having a mini-stroke late last year.

"He's not getting any better ... you have one stroke, and then it's very likely you'll have another," Mr Shipton told reporters.

"There's over 300 doctors who have written a letter advising his physical health is in decline ... mentally he's suffering psychological torture ... he is being crushed essentially.

"(It's) slow-motion murder before our eyes. If you compare what happened to journalist Jamal Khashoggi, that is what's going on to Julian in slow motion."

Independent MP Andrew Wilkie, a former intelligence analyst, questioned if Mr Albanese was backing up his words with actions.

"We can't be confident they are doing enough,'' Mr Wilkie told reporters.

"Using quiet diplomacy has its place, but only so far as it achieves an outcome, and it has not achieved an outcome.

"Our prime minister is able to pick up the phone to the UK prime minister, he is able to pick up the phone to the US president, he is able to make the case for an Australian citizen."

Noting the attendance at the parliamentary briefing brought representation from millions of Australians, Mr Wilkie said the government could not pretend Mr Assange's fight was a "niche issue" and said every day he was inside was "another day of gross injustice".

But while Labor senator Don Farrell reiterated the government's belief that the case had dragged on too long, he said it did not wish to interfere with the US and UK legal processes.

"As the PM has pointed out, not all foreign affairs is best conducted with a loudhailer or a megaphone," he said.

"Australia, of course, is not a party to Mr Assange's case ... our government, I'm advised, cannot intervene in the legal matters of another country, just like we wouldn't want those countries to intervene in our legal process."

Australian Associated Press