Lawyers for WikiLeaks founder Julian Assange said today they fear he could face execution in the United States if he is extradited to Sweden.

The 39-year-old whistleblower is wanted by the Swedish authorities over claims that he sexually assaulted two women during a visit to Stockholm in August.

But his defence team believe there is a “real risk” he could be extradited on to the US, where he could be detained in Guantanamo Bay or even face the death penalty.

The claim emerged in a skeleton argument released by Assange’s lawyers in the wake of a preparatory legal hearing at Woolwich Crown Court.

Assange’s legal team suggested that extraditing him to Sweden could breach Article 3 of the European Convention on Human Rights (ECHR), which bans torture.

They wrote: “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 risk of him being detained at Guantanamo Bay or elsewhere, in conditions which would breach Article 3 of the ECHR.

“Indeed, if Mr Assange were rendered to the USA without assurances that the death penalty would not be carried out, there is a real risk that he could be made subject to the death penalty.”

Posted on the website of Assange's British solicitor, Mark Stephens, the legal documents attack the case for extradition by the Swedish authorities.

His legal team said the case is built on an “improper purpose” because the European Arrest Warrant appears to have been created to only question Assange, not necessarily prosecute him.

They added that “mere suspicion” should not create a request for extradition, adding: “A person’s extradition should not be sought merely in order for him to be questioned.”

Solicitors also questioned whether Gothenburg prosecutor Marianne Ny is able to issue an arrest warrant and said the Swedish authorities should arrange for him to be questioned in Britain.

The skeleton argument focused on the claims of one of the alleged victims, including a text message in which the woman alleged she was “half asleep” at the time of the claimed assault.

Assange’s solicitors complained they have not been given a copy of this message and claimed the Swedish authorities have inflated the allegation to suggest she was “fully asleep”.

They said it was done “in order to support the making of a rape allegation” adding that: “This would in itself constitute prosecutorial abuse.”

The paperwork goes on to attack Swedish prosecutors for failing to disclose other text messages between the two women which “speaks of revenge and of the opportunity to make lots of money”.

The legal papers, drawn up by Geoffrey Robertson QC, claimed the Australian has been the victim of "illegal" or "corrupt" behaviour by the Swedish authorities.

Mr Robertson said his client’s name was illegally leaked to the press, resulting in his “vilification throughout the world”.

He also accused the Swedes of undertaking a “secret process” to restart the rape case after it was dropped by a prosecutor in Stockholm.

The legal document said Assange believes the extradition request has been issued to punish him for his political opinions.

Mr Robertson said there is a “real risk” that if brought to Sweden he could be extradited or illegally rendered to the United States.

The barrister said he could be imprisoned in Guantanamo Bay where he may be poorly treated and even executed.

He wrote: “Indeed, if Mr Assange were rendered to the USA, without assurances that the death penalty would not be carried out, 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.”

Mr Robertson noted how one of the alleged victims wrote a blog which several months prior to the allegations set out a seven-stage plan for revenge against an ex-lover.

The “steps” included apparent advice or plans on how to cause misery to a former partner, including sending letters and photographs to him to make it look as if the relationship continues.

Quoted in the document, the blog apparently encourages others to “use your imagination” and to “get to work”.

It added: “And remember what your goals are while you are operating, ensure that your victim will suffer the same way as he made you suffer.”

Mr Robertson said: “Clearly these text messages and extracts from blogs significantly undermine not only the prosecution’s case but the request for his extradition. Yet they have not been disclosed to Mr Assange or his legal team.”

Assange: Work will go on

Earlier, Assange said his work will "continue unabated" as the extradition battle rages on and he will step up publication of more than 250,000 leaked diplomatic cables.

He vowed that the disclosures, dubbed “Cablegate”, will continue in newspapers around the world after the full extradition two-day hearing was set for February 7.

Speaking in front of hundreds of cameramen and reporters, Assange said he was “happy” with the outcome of the 10-minute hearing.

He said: “Our work with WikiLeaks continues unabated and we are stepping up our publication of materials relating to Cablegate and other materials.

“This will shortly be occurring through our newspaper partners around the world, big and small newspapers and human rights organisations.”

Assange, who spoke in court only to confirm his personal details before listening intently, was released on conditional bail by District Judge Nicholas Evans.

He got up at 3am to travel to court from his bail address, a large manor house owned his friend Vaughan Smith on the Norfolk/Suffolk border.

The judge granted an application for Assange to be allowed to stay at the Frontline Club, in Paddington, London, founded by Mr Smith, on the nights before the next hearing.

But he said people who have contributed to the £240,000 (€288,500) bail deposit for Assange must submit written confirmation that they agree with the arrangement.

Assange denies committing any offences and his supporters claim the criminal inquiry and extradition request is unfair and politically motivated.

He recently signed a book deal for his life story as the US authorities stepped up their pressure on WikiLeaks by demanding information from Twitter.

The hearing took place at Belmarsh Magistrates’ Court, sitting at Woolwich Crown Court, where a small group of supporters gathered nearby.

The high security court has been the scene for a string of terrorism trials including the airline bomb plotters and London Glasgow suicide bomber.

Supporters of Assange including human rights campaigner Bianca Jagger, socialite Jemima Khan and Gavin MacFadyen, director of the Centre for Investigative Journalism, attended the hearing.