A UN expert says Australian Wikileaks founder Julian Assange is displaying symptoms of torture while imprisoned in Britain.

UN rapporteur on torture Nils Melzer said Saturday morning (Australian time) that Britain has taken no action since he and medical experts visited Assange at a London prison in May.

They found Mr Assange displaying “all the symptoms typical for prolonged exposure to psychological torture”.

“However, what we have seen from the UK government is outright contempt for Mr Assange’s rights and integrity,” Mr Melzer said in a statement.

“Despite the medical urgency of my appeal, and the seriousness of the alleged violations, the UK has not undertaken any measures of investigation, prevention and redress required under international law.”

Mr Assange appeared in court on Monday for a procedural hearing over a US extradition request.

The 48-year-old struggled to recall his name and age in court where a London judge refused a bid to delay his February extradition hearing.

Mr Melzer urged Britain to block the extradition and release Assange.

“Unless the UK urgently changes course and alleviates his inhumane situation, Mr Assange’s continued exposure to arbitrariness and abuse may soon end up costing his life,” Mr Melzer, said.

The US government accused Mr Assange of conspiring with former US military intelligence analyst Chelsea Manning to leak a trove of classified material in 2010.

The documents relate to the wars in Iraq and Afghanistan and to secret information on intelligence sources, the US said.

In June, the British government signed an order allowing Assange to be extradited to the US over the computer-hacking allegations.

British police dragged him out of the Ecuadorian embassy in London on April 11 after Quito ended his asylum. He had spent seven years inside the building to avoid arrest.

-with AAP