According to a brief statement on the website of the Swedish prosecution authority, the country’s director of public prosecutions, Marianne Ny, “has today decided to discontinue the investigation regarding suspected rape (lesser degree) by Julian Assange”.

The prosecutor and her deputy, Ingrid Isgren, would say more about their reasons at a press conference later on Friday, the statement said.

The Wikileaks founder sought asylum in Ecuador’s embassy in London in 2012 after losing court battles to avoid extradition to Sweden over the claims, which he denies.

A second allegation of sexual assault, made by a second Swedish woman, was dropped by Swedish authorities in 2015 after the statute of limitations expired.

With the threat of extradition to Sweden removed, the decision potentially allows the Australian, 45, to leave the embassy. However, his lawyers repeatedly said that he would not do so without assurances that he will not face extradition to the US over possible espionage charges, linked to Wikileaks’ publishing activities.

Shortly after the Swedish announcement, the Metropolitan police in London issued a statement confirming a warrant for the arrest of Assange still stands following his failure to surrender to the court on 29 June 2012. It said the service “is obliged to execute the warrant should he leave the embassy”.

It added: “Whilst Mr Assange was wanted on a European arrest warrant (EAW) for an extremely serious offence, the MPS response reflected the serious nature of that crime. Now that the situation has changed and the Swedish authorities have discontinued their investigation into that matter, Mr Assange remains wanted for a much less serious offence. The MPS will provide a level of resourcing which is proportionate to that offence.”

Shortly after the announcement, an image of Assange smiling was posted to his Twitter account.

Assange was interviewed by Isgren in the embassy in November, following a lengthy diplomatic and legal impasse between the Swedish and Ecuadorian authorities.

The announcement on Friday followed a letter sent to the Swedish government by the government of Ecuador saying there had been a “serious failure” by the prosecutor, including a “lack of initiative” to complete inquiries.

The letter raised questions over developments in the US since the election of Donald Trump as president, including a speech by the CIA director, Mike Pompeo, describing WikiLeaks as a “hostile intelligence service” and a threat to US national security.

Recent public declarations such as this constitute an “obvious risk” for Assange, said the letter.

The US attorney general, Jeff Sessions, last month said arresting Assange was a priority. There are no charges against him though media reports have suggested the US justice department is considering how to bring them.

“We’ve already begun to step up our efforts and whenever a case can be made, we will seek to put some people in jail,” Sessions said.

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