Lawyers for Swedish authorities told Britain's Supreme Court on Thursday that a bid to extradite WikiLeaks founder Julian Assangefor questioning over rape allegations is valid.

In his final appeal within the British legal system, Assange is resting his fight against extradition on the argument that the Swedish prosecutor who ordered his arrest in December 2010 was not a proper judicial authority.

But Clare Montgomery, a British lawyer acting on behalf of theSwedish authorities, dismissed the claims made by lawyers for the 40-year-old Australian on Wednesday.

She said that in conventions that were replaced in 2004 by theEuropean Arrest Warrant system -- the system under whichSweden is seeking Assange's arrest -- it was clear that public prosecutors were considered judicial authorities.

It is the second and final day of the hearing in central London before seven Supreme Court judges. They are expected to defer judgment for several weeks.

Dozens of supporters were again in court to see the white-haired former hacker, who has become a cause celebre since his anti-secrecy website enraged Washington by leaking thousands of secret US documents.

Britain's Supreme Court only deals with cases that it decides raise a wider point of public interest, which in Assange's case would be an overturning of the whole fast-track European Arrest Warrant system.

On Wednesday, Assange's lawyer Dinah Rose argued that extraditing him to Sweden on the basis of a European Arrest Warrant issued by a prosecutor would breach legal principles dating back 1,500 years.

She said that only a judge or similar official should count as a proper "judicial authority".

Rose brought in Latin references and discussed the justice systems of a host of European countries including France, Germany, Ireland and the Netherlands as they tried to convince the judges.

Assange has spent most of the last year under virtual house arrest at the mansion of a supporter in eastern England.

Assange denies the rape and sexual assault allegations made by two women in Sweden, and insists the sex was consensual.

He has also claimed that the allegations against him are politically motivated. Assange has said he fears he will eventually be handed over to the United States, where Bradley Manning, a US soldier accused of handing documents to WikiLeaks, faces a court-martial.

If the court rejects his appeal, Assange will have exhausted all his options in Britain but he could still make a last-ditch appeal to the European Court of Human Rights (ECHR), prosecutors have said.

But if Assange wins his case it could call into question the whole European Arrest Warrant system.

While the legal battle has dragged on, Assange's celebrity status has grown.

He is to host his own TV show, although Russia's state-run RT is the only channel to confirm it will broadcast it. He will also make an appearance as himself later this month on the 500th episode of the US cartoon show Simpsons.

A lower court in Britian initially approved Assange's extradition to Sweden in February 2011. An appeal to the High Court was rejected in November, but he subsequently won permission to appeal to the Supreme Court.