Judge warns WikiLeaks founder Julian Assange he is almost certain to be extradited to Sweden to face sex assault claims

The WikiLeaks founder, Julian Assange, walked free after nine days in jail last night when a high court judge released him on bail. However, the judge warned him that he is almost certain to be extradited to Sweden to face sex assault allegations.

The court refused an attempt by the Crown Prosecution Service to stop Assange being freed, but imposed tougher bail conditions than previously outlined by a lower court, which meant his lawyers had to scramble to meet them before he was returned to prison for another night.

Finally Assange emerged on to the steps of the high court at 5.46pm, as snow began to fall, to make a defiant statement and to thank his supporters.

"I hope to continue my work and to continue to protest my innocence in this matter and to reveal, as we get it, as we have not yet, the evidence from these allegations," he said.

As well as the prospect of a trial in Sweden, there is a growing consensus among US constitutional lawyers and other legal experts that Assange will be indicted by Washington. After his release he said that even if he were indicted in the US, the spilling of state secrets would continue. He said that WikiLeaks was a "resilient organisation" that could "withstand decapitation attacks".

Last week City of Westminster magistrates remanded Assange in custody because they said he posed too high a danger of absconding. On Tuesday his lawyers won a reversal of that decision, with a judge granting him bail on tough conditions – but the CPS appealed.

Yesterday at the high court Mr Justice Ouseley rejected the CPS argument that there were no conditions a judge could impose that would stop Assange from fleeing. He ordered the CPS to pay costs but imposed new conditions on Assange.

His bail will see him stay at Ellingham Hall in Norfolk, owned by Vaughan Smith, a former army captain, who was approved to provide surety at Tuesday's hearing along with the restaurant designer Sarah Saunders. While at the mansion, Assange must observe a curfew and be tagged. He will have to report daily to a police station, and £200,000 in security, raised by his supporters, has been paid into the court.

But there are no restrictions now on his access to the internet or communications, meaning he is much more able to defend himself and WikiLeaks from US anger.

The legal victory for Assange yesterday was a small step in what is likely to be a long battle. Ouseley warned him that the Swedish warrant was likely to be upheld, and that he would be extradited to face a trial for the alleged attacks. Assange's mother, Christine, who was in court, said she was "very, very happy". She added: "I can't wait to see my son and to hold him close. I had faith in the British justice system to do the right thing, and that faith has been confirmed today."

For hours, it was far from certain that Assange's supporters and lawyers would manage to get him out in time. They had struggled to track down five more people the judge had approved as guarantors that Assange will observe his strict bail conditions. Some had to go to City of Westminster magistrates to sign the official paperwork and others who were out of London had to go to nominated police stations.

Among those approved by the high court to act as surety were the Nobel prize winner Sir John Sulston, Lord Evans, an ex-Labour minister and former chairman of Faber & Faber, and the Marchioness of Worcester. Ouseley said he was concerned that some on the list of people willing to act as surety were doing so because they supported WikiLeaks, and would think a greater cause had been served if Assange skipped bail to avoid trial in Sweden.

He warned Assange that if he tried to flee he would be "found to have exploited quite ruthlessly those who have put their trust in him and to have let them down".

On Channel 4 News last night, Assange maintained he was the victim of a conspiracy orchestrated by the US with the assistance of the Swedish intelligence service.

"There is an ongoing attempt by the US to extradite me to the US and that extradition is much more likely to occur if I am already in Sweden."

He said his Swedish legal team had now been passed evidence relating to the rape charges against him. "There has never been a single page provided to me in English and, until two weeks ago, not a single page whatsoever provided in any form to my Swedish counsel – even in Swedish. This is a clear, clear abuse of process."

Assange later described the rape allegations against him as "a very successful smear campaign and a very wrong one". Speaking on BBC 2's Newsnight, he said information relating to accusations had been leaked either by "the Swedish prosecution service or some organisations that have obtained selective material".

He said: "My lawyers informed me this afternoon there will be another smear attempt relating to this investigation some time tomorrow."

Speaking outside Ellingham Hall later, Assange said his lawyers in Sweden had got hold of 100 pages of material related to the allegations but he had yet to receive a comprehensive English translation.

He said there could also be an attempt by the US to charge him with spying.

"We have heard today from one of my US lawyers, yet to be confirmed, but a serious matter, that there may be a US indictment for espionage for me, coming from a secret US grand jury investigation," he told Sky TV.

"Obviously it is extremely serious, and one of the concerns that we have had since I have been in the UK is whether the extradition proceeding to Sweden, which is occurring in a very strange and unusual way, is actually an attempt to get me into a jurisdiction which will then make it easier to extradite me to the United States."