Assange appeals against UK extradition decision

Wikileaks founder Julian Assange arrives at the Supreme Court in Westminster, on the second day of his extradition appeal, in central London, February 2, 2012.

LONDON (Reuters) - WikiLeaks founder Julian Assange has appealed against Britain's Supreme Court's decision to back his extradition to Sweden over alleged sex crimes.

Two weeks ago, judges at Britain's top court rejected his argument by a 5-2 majority that a European arrest warrant for his extradition was invalid, seemingly putting an end to an 18-month legal battle.

However, his lawyers argued that some of the judges had reached their decision based on a legal point that had not been argued in court, preventing the defense team from making a counter-submission.

The court agreed to give Assange 14 days to challenge the decision and a spokeswoman said on Tuesday that an appeal had been submitted.

"No time has been set to look at the evidence," the spokeswoman said. "We are hoping it will be done promptly."

The former computer hacker gained international prominence in 2010 when WikiLeaks began releasing secret video footage and thousands of U.S. diplomatic cables about Iraq and Afghanistan, in the largest leak of classified documents in U.S. history.

That made him a hero to anti-censorship campaigners but Washington was furious about the release of classified documents.

Swedish prosecutors want to question Assange over allegations of rape and sexual assault made by two female former WikiLeaks volunteers. He denies any wrongdoing and has been fighting extradition since his arrest in Britain in December 2010.

His lawyers argue the European arrest warrant was invalid because it was issued by a prosecutor and not a judge or a court, as required in Britain. Prosecutors say different legal procedures are allowable under the internationally agreed format.

Even if he loses the appeal in Britain, the Australian could take his case to the European Court of Human Rights, potentially holding up the extradition process for months.

(Reporting by Michael Holden; Editing by Jon Boyle)