British lawyers for WikiLeaks founder Julian Assange accused Swedish prosecutors of "corrupt" behaviour in their efforts to extradite him over allegations of sex crimes, defence papers revealed Tuesday.

His legal team also says there is a "real risk" that if extradited to Sweden, Assange may be sent on to the United States, where the papers say he could be detained at Guantanano Bay or even face the death penalty.

The claims are contained in lawyer Geoffrey Robertson's provisional skeleton argument, which Assange's team will use to fight the extradition request during a hearing at a London court on February 7-8.

In the document, released after a brief hearing on Tuesday, Robertson contests Swedish prosecutor Marianne Ny's right to issue a European arrest warrant, which prompted British police to arrest Assange on December 7.

Assange was bailed on December 16.

Robertson questions the credibility of the alleged victims, accuses Swedish prosecutors of illegal behaviour and warns Assange could be sent to the United States, where he has been vilified over WikiLeaks' release of secret US cables.

"Mr. Assange has been the victim of a pattern of illegal and/or corrupt behaviour by the Swedish Prosecuting Authorities," the document says.

It claims that prosecutors acted illegally by releasing his name to the press and leaking evidence against him, and that they refused to accept his repeated offers to give an interview before the warrant was issued.

Elsewhere in the skeleton argument, Robertson claims that Ny did not have the right to issue a European arrest warrant, saying that only the Swedish national police board can issue such warrants.

And he said it should not have been issued when Assange was only wanted for questioning about the alleged sexual assault of two women, insisting that "mere suspicion should not found a request for extradition".

The draft argument also says there has not been full disclosure of the evidence, including text messages between the alleged victims which "speak of revenge and the opportunity to make lots of money".

The document further repeats Assange's argument that the allegations against him are linked to the WikiLeaks disclosures.

"It is submitted that there is a real risk that, if extradited to Sweden, the US will seek his extradition and/or illegal rendition to the USA, where there will be a real risk of him being detained at Guantanamo Bay or elsewhere," Robertson says.

He adds: "There is a real risk that he could be made subject to the death penalty. It is well-known that prominent figures have implied, if not stated outright, that Mr. Assange should be executed."