Pamela Anderson has cancelled a visit to see WikiLeaks founder Julian Assange in prison due to a “personal emergency”.

The actor was due to visit Mr Assange on Tuesday, before holding a press conference outside Belmarsh Prison in southeast London.

A statement from the Don’t Extradite Assange campaign said: “Pamela has a personal emergency which has meant she has had to go home and cancel everything for the next two weeks.”

Anderson says Mr Assange has been subjected to “traumatic psychological torture”, as she urged his home country Australia to stop him being extradited to the US.

The former Baywatch star – one of Assange’s most high-profile supporters – visited him in jail earlier this year.

She recently said she was “extremely distressed at the thought of his declining state” and added that her heart broke for him.

Anderson tweeted that Mr Assange was “hanging on like a super hero” in Belmarsh, where he was sent earlier this year after spending seven years in the Ecuadorean embassy in London to avoid extradition.

Mr Assange was jailed for 50 weeks in May for breaching his bail conditions after going into hiding to avoid extradition to Sweden over sex offence allegations.

He faces 18 charges in the US, including allegations that he conspired to break into a Pentagon computer and worked with former US army intelligence analyst Chelsea Manning to leak hundreds of thousands of classified documents.

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

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.

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

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

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

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

“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,” she said.

“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 prison conditions.

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

Speaking outside court, a member of Mr Assange’s team said the computer was unlikely to have internet access for research.

District Judge Baraitser remanded Assange in custody ahead of a substantive case management hearing next month.

He will also 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.