Lawyers for Julian Assange have claimed victory after a Swedish prosecutor bowed to pressure from the courts and agreed to break the deadlock in the WikiLeaks founder’s case by interviewing him in London.

Marianne Ny, who heads the investigation into accusations of rape, coercion and sexual molestation against Assange, made a formal request to interrogate him in the Ecuadorian embassy – the first sign of movement in a case that has been frozen since August 2012.

The prosecutor will also ask the UK government and Ecuador for permission to carry out the interviews at the embassy in London, where Assange has been staying for more than two-and-a-half years to avoid extradition to Sweden, from where he fears being handed over to the US to face espionage charges.

Ny said she had changed her mind because the statute of limitations on several of the crimes of which Assange is suspected runs out in August 2015.

“My view has always been that to perform an interview with him at the Ecuadorian embassy in London would lower the quality of the interview, and that he would need to be present in Sweden in any case should there be a trial in the future. This assessment remains unchanged,” Ny said in a statement.

“Now that time is of the essence, I have viewed it therefore necessary to accept such deficiencies to the investigation and likewise take the risk that the interview does not move the case forward, particularly as there are no other measures on offer without Assange being present in Sweden.”

Per Samuelson, a Stockholm lawyer for Assange, said: “It is a victory for us. We have been asking for this to happen for over four years. That is the route to acquittal.”

There were minor details to be discussed between Assange and the prosecutor over how the interrogations will be conducted, Samuelson said, “but there are no major questions as I see it”. Assange welcomed the development but was irritated it had taken so long, Samuelson said. They are due to meet in London on Saturday.

The British Foreign Office said in November it would welcome a request by the Swedish prosecutor to question Assange inside the Ecuadorian embassy. Ecuador’s government has also repeatedly stated that it approves of such a step. Assange has been wanted in Sweden since the accusations were made against him in August 2010.

His lawyers, who are currently appealing against his arrest warrant in Sweden’s highest court, have complained bitterly about the prosecutor’s refusal to travel to London to speak to him – an essential step under Swedish jurisprudence to establish whether Assange can be formally charged.

The prosecutor’s refusal, they say, has condemned Assange to “severe limitations” on his freedom that are “disproportionate” to the accusations against him.

Julian Assange appeals to Sweden's supreme court over arrest warrant Read more

Ny has objected that interrogating Assange abroad would be complicated and largely pointless because – should sufficient grounds emerge – he would still have to travel to Sweden for trial. However, she is obliged to drop the case against him unless she believes there are reasonable grounds for suspicion of his guilt.

The prosecutor’s apparent U-turn on Friday came just days after a supreme court judge in Stockholm wrote to the prosecutor general, directing him to give his opinion concerning Assange’s appeal, “especially regarding the investigatory procedure and the principle of proportionality”.

Further pressure on the prosecutor came in November when the appeal court, while rejecting Assange’s arguments, nonetheless directed sharp criticism at Ny for failing in her obligation to move the case forward.

Swedish legal opinion at a senior level has swung against the prosecutor’s position. Anne Ramberg, the head of Sweden’s Bar Association, welcomed the decision to go to London, but added: “It should have been taken long before.”

Karin Rosander, Ny’s spokeswoman, said the decision to go to London was entirely her own. She said: “Swedish prosecutors are independent in their decision-making and nobody, not even the prosecutor general, can order a prosecutor what steps to take.”



Elisabeth Massi Fritz, a lawyer for one of the women in the case, said she had changed her mind on questioning Assange in London, and her client had also requested the move. “If Swedish investigators and prosecutors are present when Assange is interviewed, then it will be a good interrogation of high quality,” she said.

Last year, Fritz dismissed as “empty and ill-informed speculation” calls by Swedish politicians and top legal figures to go to London.

Questioning the prosecutor’s reluctance to travel to London, several Swedish legal figures have pointed to the occasion in 2012 when the entire Stockholm district court moved to Kigali for several weeks to interview witnesses to the Rwandan genocide, with more witnesses heard in Stockholm by video link from Kigali.

The proposed interviews in London will be conducted by the deputy prosecutor in the case, Ingrid Isgren, and a police investigator. The statute of limitations on the rape accusations against Assange expires in August 2020.

Sweden’s supreme court is due to rule on the case later this month or next.

The prosecutor’s change of heart was “demonstrably cynical” in waiting until shortly before the statute of limitations expired to keep Assange “trapped in the UK”, said journalist John Pilger for the Julian Assange Legal Defence Fund.

Ecuador’s foreign ministry said in a statement: “We welcome the decision of the Swedish authorities to finally interview Julian Assange in our London embassy. The government of Ecuador has repeatedly made this offer since 2012, when it granted asylum to Mr Assange.

“This decision could have been taken from the beginning, and not only when the case is about to be subject to statute of limitation. It is a great injustice that Mr Assange, due to the prosecutors’ failure to fulfil their duty, has been deprived of freedom without charge in the United Kingdom, and confined in our embassy for almost 1,000 days. This amounts to a violation of his human rights, at great personal cost to him and his family.”

• This article was amended on 19 June 2015 to clarify quotes from Marianne Ny. The earlier version included the Guardian’s own translation from her statement in Swedish. These have been replaced with an English version of the statement issued by Ny’s office.