WikiLeaks founder Julian Assange has asked the High Court to block his "legally flawed" extradition to Sweden over sexual assault allegations.
Lawyers for Assange challenged a ruling by District Judge Howard Riddle at Belmarsh Magistrates' Court in south London that extradition should go ahead.
Ben Emmerson QC, appearing for Assange, 40, told two judges the European arrest warrant (EAW) on which he was being held was flawed because it failed to provide "a fair, accurate and proper" description of the alleged sexual misconduct.
Mr Emmerson also argued Assange was a victim of a "philosophical and judicial mismatch" between English and Swedish law on what constituted sex crimes.
Assange says the allegations against him are politically-motivated, particularly after the WikiLeaks website published a mass of leaked American diplomatic cables that rocked the US government.
He said nothing as he arrived at the court in London with lawyers. A handful of supporters gathered outside the entrance to greet him.
Assange hosted a lavish 40th birthday party at the weekend attended by celebrity guests and supporters.
Although not charged, the Australian computer expert is wanted by the Swedish prosecution authority to answer questions on three allegations of sexual assault and one of rape, said to have been committed in Stockholm last August. The accusations were made by two female WikiLeaks volunteers.
In a case which has drawn international interest, Lord Justice Thomas and Mr Justice Ousely are being asked by Assange's legal team to rule that his sexual encounters with the women were "consensual" and the alleged offences are not extradition offences.
Assange has expressed fears that extradition to Sweden could be a stepping stone to being sent to the US to stand trial on fresh charges relating to WikiLeaks, and he could even face the death penalty.