Australian MPs Andrew Wilkie and George Christensen have raised concerns over Julian Assange's mental wellbeing after meeting with him in a British jail.

Key points: Australian MPs said Assange's mental state reflected his long period of isolation

Australian MPs said Assange's mental state reflected his long period of isolation WikiLeaks editor-in-chief Kristinn Hrafnsson said Assange was taken from isolation thanks to pressure from fellow inmates

WikiLeaks editor-in-chief Kristinn Hrafnsson said Assange was taken from isolation thanks to pressure from fellow inmates The Wikileaks founder's US extradition hearing starts next week

Mr Wilkie and Mr Christensen, who are both part of the Bring Assange Home parliamentary group, spent over an hour with the WikiLeaks founder at London's Belmarsh prison, where he is being held ahead of an US extradition hearing next week.

Assange has been held there since he was dragged out of the Ecuadorian embassy in London last April and arrested for skipping bail.

Prior to that he had spent seven years inside the embassy after seeking asylum in 2012, and Mr Christensen said his lack of exposure to the outside world showed.

"It was kind of state you'd expect from a man who has been absolutely and utterly isolated and who doesn't know what has been going on," he said.

"It was clear to us that his mental state isn't good."

Queensland Nationals MP George Christensen assessed Assange's condition inside the prison. ( ABC News: Tim Stevens )

Mr Wilkie echoed Mr Christensen's assessment.

"I'm not a psychologist. but it was obvious that there's a man who's under enormous pressure," he said.

"Clearly his health and mental health has deteriorated during what is effectively years in captivity."

The 48-year-old is fighting extradition to the US, where he faces 18 charges including conspiring to hack government computers and violating an espionage law, and Mr Wilkie said if Assange is found guilty it would almost amount to a death sentence.

"If he is convicted of those charges he faces up to 175 years in a US federal prison," he said.

"It's a life sentence and it could be said to almost a death sentence."

Andrew Wilkie is one of 14 MPs in the Bring Assange Home parliamentary group. ( ABC News: Andrew Greaves )

Mr Christensen said he believes information that will come to light during the extradition hearing may change people's views on Assange and he called on the Australian government to do more to bring him home.

"I think that there's information that I now know that will be known next week that will probably make people sit up straight and worry about this a hell of a lot," he said.

"I think now is a time that the Government that I am a part of needs to be standing up and saying to both the UK and the US, 'Enough is enough, leave our bloke alone and let him come home'."

Yesterday, Mr Wilkie met with UK Opposition leader Jeremy Corbyn, who said he has sensed a shift in the UK's view on extradition in the light of another high-profile case involving the wife of a US diplomat.

Andrew Wilkie (left) met with the British Opposition Leader ahead of visiting Julian Assange at Belmarsh Prison. ( ABC News: Andrew Greaves )

Earlier on Tuesday, WikiLeaks editor-in-chief Kristinn Hrafnsson had said Assange's health was improving after he was taken out of solitary confinement.

"I saw him about 10 days ago," Mr Hrafnsson told a news conference ahead of an extradition hearing that starts next week.

"He has improved thanks to the pressure from his legal team, the general public, and amazingly, actually from other inmates in Belmarsh Prison, to get him out of isolation."

John Shipton, Julian Assange's father, is in London with his daughter to support his son and his battle against extradition. ( ABC News: Andrew Greaves )

Assange's father, John Shipton, said his son's long confinement indoors had damaged his health.

"The ceaseless anxiety that Julian's been under for now 10 years has had a profoundly deleterious effect," he told BBC television on Tuesday.

"I imagine that he will be really worried because being sent to the United States is a death sentence."

Last November, more than 60 doctors wrote an open letter saying they feared Assange's health was so bad he could die in jail.

In the letter to British Home Secretary Priti Patel, the doctors say Assange suffers from psychological problems including depression as well as dental issues and a serious shoulder ailment.

Julian Assange spent seven years holed up in the Ecuadorian Embassy in London. ( Reuters: Peter Nicholls )

ABC / Reuters