Sweden’s existing warrant to extradite Julian Assange over a sexual assault allegation would be the first consideration for the British government if the Australian were to leave the Ecuadorean embassy, Home Office sources have indicated.

Arresting Julian Assange is a priority, says US attorney general Jeff Sessions Read more

The US attorney general, Jeff Sessions, said on Thursday that the arrest of the WikiLeaks founder was now a “priority”. US federal prosecutors were understood to be considering bringing charges against Assange over a number of the website’s publications since 2010, US media reported, which could potentially lead to a second extradition request for Assange, from Washington.

Were that to happen, the question of which warrant would then take priority - from Sweden or the US - would then come into play.

However the British authorities stressed the UK had an existing legal obligation to extradite Assange to Sweden under the European arrest warrant. The Home Office never confirms whether an extradition request has been made or received until the person in question has been arrested, the source indicated – this is currently impossible while Assange remains in the embassy, where he was granted asylum in 2012.

Extradition law is notoriously complex, with requests to the UK from outside the EU governed by the Extradition Act 2003. It states that in the event of competing warrants from two countries, the home secretary would have to decide which took precedence, based on factors including the relative seriousness of the offences, the date the requests were received, and whether the person had been accused or convicted.

The government would not be able to take into account political or human rights issues, however, which would be for the courts to decide.

The US authorities cannot touch Assange while he remains in the embassy seeking to avoid an arrest warrant on rape allegations in Sweden. Ecuador’s incoming president, the socialist Lenín Moreno, has promised not to extradite him.

Barry Pollack, Assange’s lawyer, denied any knowledge of any imminent prosecution. “We’ve had no communication with the Department of Justice and they have not indicated to me that they have brought any charges against Mr Assange,” he told CNN. “They’ve been unwilling to have any discussion at all, despite our repeated requests that they let us know what Mr Assange’s status is in any pending investigations. There’s no reason why WikiLeaks should be treated differently from any other publisher.”

US authorities have been investigating Assange and WikiLeaks since at least 2010, when the website released, in cooperation with publications including the Guardian, more than a quarter of a million classified cables from US embassies, which were leaked by US army whistleblower Chelsea Manning.

Asked whether it was a priority for the justice department to arrest Assange “once and for all”, Sessions told a press conference in El Paso, Texas: “We are going to step up our effort and already are stepping up our efforts on all leaks. This is a matter that’s gone beyond anything I’m aware of. We have professionals that have been in the security business of the United States for many years that are shocked by the number of leaks and some of them are quite serious.”

He added: “So yes, it is a priority. 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.”