LONDON: Wikileaks founder Julian Assange has started his latest legal action at the Supreme Court in London to try to block his extradition to Sweden, BBC reported.
The appeal is based on whether the Swedish prosecutor who issued the European Arrest Warrant against him had the judicial authority to do so.
Assange is wanted by the Swedish authorities for questioning over alleged sex offences, which he denies.
Judgment was expected to be reserved to a later date, according to the BBC.
The key legal question for the seven judges is whether the prosecutor who issued the arrest warrant had the judicial authority to do so under provisions of the 2003 Extradition Act.
Assange's lawyer, Dinah Rose QC, said it was "a matter of fundamental legal principle" that the person issuing such a warrant was both independent and impartial.
She said the Swedish prosecutor was a party in the Assange case and therefore was not either of these things.
Rose submitted: "Since the Swedish prosecutor cannot fulfil those conditions, she is not a judicial authority and not capable of issuing a warrant for the purposes of 2003 Act."
The arrest warrant itself was therefore invalid, the BBC quoted her as saying.
Parliament believed the European Arrest Warrants (EAWs) would only be issued by judges, as stated in Part 3 of the 2003 Act, Rose added.
But she said Britain had received EAWs from bodies that were clearly not "judicial".
The High Court, which previously approved his extradition, had recognised that the status of the public prosecutor was debatable.
The 40-year-old Australian, who remains on conditional bail in Britain, claims the allegations against him are politically motivated.
He is accused of raping one woman and "sexually molesting and coercing" another in Stockholm in August 2010.
Assange's Wikileaks website published a mass of material from leaked diplomatic cables embarrassing several governments.