Julian Assange is unable to work on his extradition case because he has been given an unsuitable computer in prison, a court has heard.

The 48-year-old WikiLeaks founder is accused of leaking US government secrets in one of the largest breaches of confidential information.

Appearing at Westminster Magistrates’ Court via video-link on Monday, Assange wore a grey prison-issue jumper and spoke only to confirm his identity.

Assange had his white hair slicked back and appeared to have stubble. He wore thin-rimmed glasses which he cleaned on his top before the judge entered.

During Monday’s five-minute hearing, attended by supporters including his father, John Shipton, Assange’s remand in HMP Belmarsh was extended.

Julian Assange extradition
Julian Assange’s father John Shipton outside Westminster Magistrates’ Court (Jess Glass/PA)

He was set to be released from the high-security prison in September but was remanded in custody due to fears that he would abscond after he spent nearly seven years in the Ecuadorean embassy in London.

Gareth Peirce, representing Assange, told the court that her client was unable to adequately prepare for his “very challenging case” as the computer he had been given was not suitable.

Ms Peirce said: “I will put it on the record, you will understand that we are working extremely hard on this very challenging case; however, the most important of the impediments that we are facing is Mr Assange’s ability to access what he needs to work on his own case.

“After months of battle he was provided with a computer but it is not the sort of computer needed to work on the case.”

District Judge Vanessa Baraitser said she had no jurisdiction over the prison conditions.

Ms Peirce replied that she wanted to “exert pressure as best we can” on Belmarsh to improve the computer facilities.

Speaking outside court, a member of Assange’s team told the PA news agency that the computer was unlikely to have internet access needed for research.

District Judge Baraitser remanded Assange in custody ahead of a substantive case management hearing on December 19.

He will appear again at Westminster Magistrates’ Court on December 13 to confirm his remand in prison again before he ultimately appears for full extradition proceedings in February.