Julian Assange has been told there can be no delay in his US extradition case, as he appeared in court in London.

The WikiLeaks founder’s legal team requested more time to submit evidence and the postponement of the full extradition hearing, while claiming the charges against him were politically motivated, at a case management hearing at Westminster magistrates court.

After the defence and prosecution clashed over the timetabling of the hearings and their allocated timeframes for evidence submission, the district judge Vanessa Baraitser refused to extend the expected proceedings and told Assange his full extradition case would begin on 25 February.

Later, she asked Assange if he had understood events in court. “Not really. I can’t think properly,” he appeared to say. “I don’t understand how this is equitable. This superpower had 10 years to prepare for this case and I can’t access my writings. It’s very difficult where I am to do anything but these people have unlimited resources.

“They are saying journalists and whistleblowers are enemies of the people. They have unfair advantages dealing with documents. They [know] the interior of my life with my psychologist. They steal my children’s DNA. This is not equitable what is happening here.”

Mark Summers, defending Assange, claimed the US had been spying on his client and said there was a link between the “reinvigoration of the investigation and Donald Trump’s presidency”.

“This is part of an avowed war on whistleblowers to include investigative journalists and publishers,” Summers said. “The American state has been actively engaged in intruding on privileged discussions between Mr Assange and his lawyer.”

He referred to reports that Spanish courts are investigating a security company that allegedly worked in conjunction with the US to “obtain information by unlawful acts, thefts and clandestine surveillance within the Ecuadorian embassy … with increasing intensity from 2017 onwards”, and asked for more time to prepare evidence for the case.

The prosecutor James Lewis QC, representing the UK government, said he strongly opposed Assange being given more time to prepare evidence, pre-empting their later request.

Assange, 48, faces extradition to the US over allegations he conspired to break into a classified Pentagon computer and could receive a 175-year jail sentence if convicted.

As he entered the dock, on his third public appearance since his arrest in April, people in the packed public gallery raised their fists in solidarity. The former London mayor Ken Livingstone and the journalist John Pilger were among those in attendance.

Afterwards, the German Bundestag member Heike Hänsel echoed warnings from Amnesty International and warned of a bleak future for journalists publishing “truthful information” contrary to US interests.

“The British government and the EU must both reject this extraterritorial political persecution,” she said.

WikiLeaks said Assange was being kept in isolation without access to legal papers, a computer or “meaningful participation in his case” and that the conditions were significantly obstructing his legal defence.

The site’s editor-in-chief, Kristinn Hrafnsson, said the case should be thrown out immediately, adding: “Not only is it illegal on the face of the treaty, the US has conducted illegal operations against Assange and his lawyers which are the subject of a major investigation in Spain.”

Court proceedings continued while a protest attended by about 100 activists chanting “Free Julian Assange” and “No extradition, there’s only one decision” took place outside.

After the hearing, a van believed to be returning Assange to prison was approached by his supporters who slapped the sides of the vehicle.

Assange's supporters converge on van thought to be returning the Wikileaks founder to Belmarsh prison pic.twitter.com/qaHzM4tBA7 — Mattha Busby (@matthabusby) October 21, 2019

Assange last appeared in court in May, when he was jailed for 50 weeks for skipping bail by going into hiding in the Ecuadorian embassy in London in 2012. Back then he was facing extradition to Sweden, where he was wanted in connection with sexual offence allegations.

He was remanded in custody in April after Ecuador revoked his political asylum, before the then home secretary, Sajid Javid, signed an order allowing Assange to be extradited to the US over the allegations. There are concerns over his health, and he has spent time on a medical ward in prison.

Information released by WikiLeaks revealed the extent of state surveillance in western countries and the conduct of the US troops in the Middle East, which Assange alleged proved war crimes had been perpetrated.