Prosecutors accused of gross breach of law by not travelling to UK to interview WikiLeaks founder in Ecuadorian embassy

Swedish lawyers for Julian Assange have argued that prosecutors are in "gross breach of Swedish law", as they lodged an appeal in a fresh attempt to break the deadlock that has seen the WikiLeaks founder begin his third year living in the Ecuadorian embassy in London.

"Julian Assange has been kept under house arrest for two years with no medical treatment, no sunshine, no family, no nothing, and this harm should be taken into account when applying Swedish law," Per Samuelsson, a lawyer for Assange in Stockholm, told the Guardian.

In July, a Stockholm judge ruled that Sweden's prosecutor had sufficient cause to continue to pursue the arrest of Assange in order to question him about the crimes of which he is suspected. On Friday, his lawyers lodged their anticipated appeal against this ruling.

No charges have yet been brought against Assange in Sweden, because he has not been interrogated by police regarding the allegations brought by the second of the two women. The prosecutor insists Assange come to Sweden for questioning over the allegations of sexual molestation and rape involving the women whom he met during a visit to the country in 2010.

"We have analysed the decision of the district court and deepened our legal arguments on those points where we think the court is wrong," Samuelsson said.

The lawyers argue that there is a "collision of norms" between Ecuador's decision to grant Assange asylum and Sweden's move to issue an arrest warrant. Neither can be implemented, creating a deadlock.

"Because this can go on for several years, it does the Swedish state no good at all, but harms Julian Assange severely," Samuelsson said.

A spokesperson for Sweden's chief prosecutor, Marianne Ny, said she had not yet received the appeal so could not comment on it. But, the spokesperson added, Ny remained of the view that "Julian Assange has chosen to evade the criminal justice system by seeking asylum in the Ecuadorian embassy … he should make himself available for interview and, if needed, trial for the offences to which he is suspected of in Sweden."

Assange's lawyers argue that Sweden's prosecutor "is in gross breach of Swedish law" by not travelling to London to interrogate Assange.

"This is harming both of the women [plaintiffs], destroys the value of oral evidence, keeps evidence secret from the defence, and makes it impossible for Julian Assange to explain to the prosecutor and to Sweden that he is innocent, because he is forbidden to add his version to the preliminary investigation," Samuelsson said.

The case will now go to the court of appeal. A judge is likely to decide next week whether to hold an oral hearing or to rule on the case based only on the documents available, according to a spokesperson for Stockholm district court.

Oral hearings are rare, but Assange's lawyers said it would be wrong for the judge to deny their request because documents regarding an "important piece of evidence" – text messages sent by the plaintiffs in August 2010 – are being withheld by the prosecution and can only be read out to the judge in open court.

The lawyers have also objected over the district court's refusal to take into account the time that has passed since Assange entered the Ecuadorian embassy in June 2012, which the court said he chose to do himself.

At a fevered press conference last month, Assange said cryptically that he intended to leave the embassy soon. But his Swedish lawyers said it would be wrong to see that remark as being connected to the appeal.

"As soon as his right to asylum is respected, Julian Assange will leave the embassy, but he does not have any plans to waive that right," Thomas Olsson, Assange's second lawyer in Stockholm, said.

Sweden is in the final days of a closely fought general election campaign in which feminist demands have had a high profile on the left and the right. A change of government is likely after Sunday's poll.

Samuelson hinted that the decision to file the appeal on Friday may have been connected to the election. "It is not a coincidence," he said.