The whistleblowing website WikiLeaks said last night it would not to be gagged by the imprisonment of its founder, Julian Assange, after a judge refused him bail at a dramatic extradition hearing in London.

Assange, 39, who is wanted in Sweden over claims he sexually assaulted two women, was in Wandsworth prison last night after district judge Howard Riddle ruled there was a risk he would fail to surrender if granted bail. Assange denies the allegations.

Despite Jemima Khan, former wife of Pakistan cricket captain Imran Khan, the campaigning journalist John Pilger, the film director Ken Loach and others offering to stand surety totalling £180,000, the judge said the Australian Assange's "weak community ties" in the UK, and his "means and ability" to abscond, represented "substantial grounds" for refusing bail.

He was remanded until 14 December, when the case can be reviewed at the same court. His legal team said he would again apply for bail at that hearing.

Last night Kristinn Hrafnsson, a spokesman for WikiLeaks, confirmed it would continue publishing US diplomatic cables. In a statement he said: "This will not stifle WikiLeaks. The release of the US embassy cables – the biggest leak in history – will still continue. We will not be gagged, either by judicial action or corporate censorship."

WikiLeaks volunteers met in London last night to finalise plans for how the organisation would operate without Assange. The majority of staff would continue to work on the publication of the US embassy cables while a small group concentrates on campaigning for his release.

WikiLeaks staff will today move into a London office, having spent weeks commuting between the capital and the home counties bolthole from which Assange has been co-ordinating the release of the leaked cables. Staff had been required to take elaborate measures to ensure they were not followed to Assange's location and use of mobile phones was banned to avoid detection.

A WikiLeaks source said last night that Assange had been unprepared for being taken into custody, expecting that he would be granted bail. "We thought he'd be out. All he's got is the suit he was sitting in the box in," the source said.

The source added that although Assange was exhausted, he remained "together, positive and strong" after he was refused bail. It is understood his lawyers have requested that he be held alone.

The refusal to grant Assange bail came on a day when increasing pressure was brought to bear in the US on companies and organisations with ties to WikiLeaks.

As Joe Lieberman, chairman of the Senate's homeland security committee, urged businesses to sever their ties with the website, Visa suspended the payment of donations to the website through its credit card.

Asked about the New York Times's role in publishing the leaked cables, Lieberman told Fox news the newspaper "has committed at least an act of bad citizenship. Whether they have committed a crime I think bears very intensive inquiry".

Michael Mukasey, a former US attorney general, said last night that American lawyers should try to extradite Assange to the US for betraying government secrets. "If I was still in charge there would have been an investigation," he told the BBC's Newsnight. "This is a crime of a very high order. Julian Assange has been leaking this information. He came into possession of it knowing that it was harmful."

Mukasey, who stepped down from the post of attorney general last year, implied that the Swedish sexual accusations may only be a holding charge. "When one is accused of a very serious crime," he said, "it's common to hold him in respect of a lesser crime … while you assemble evidence of a second crime."

Assange, wearing a black suit and open-necked white shirt, stood in the glass-panelled dock at Westminster magistrates yesterday as more than 50 journalists from around the world packed into the well and more than 20 supporters and friends crammed into the public gallery. Outside, the pavement was swallowed up as more photographers and camera crew jostled with protesters gathered at the building's main entrance.

After the ruling – with supporters waving A4 printouts reading "Character Assassination" and "Protect Free Speech" – his solicitor, Mark Stephens, emerged from court to claim the prosecution was "politically motivated" and pledged WikiLeaks would not be cowed. Assange was entitled to a high court appeal, he said, adding the judge was "impressed" with the number of people prepared to "stand up" on his client's behalf. "[Those supporters] were but the tip of the iceberg," he said. "This is going to go viral. Many people believe Mr Assange to be innocent, myself included. Many people believe that this prosecution is politically motivated."

Pilger, who told the judge he knew Assange and had "very high regard for him", said outside court: "Sweden should be ashamed. This is not justice – this is outrageous."

Assange was arrested by appointment at a London police station at 9.20am after a European arrest warrant was received by the Metropolitan police extradition unit yesterday. He appeared in court at 2pm, where he spoke to confirm his name and date of birth and to tell the court: "I do not consent to my extradition."

There was confusion when he initially refused to give an address except a Post Office box number. When told this was unacceptable, his lawyer, John Jones, read out an address at 177 Grantham Street, Parkville, Victoria, Australia. Assange is wanted in connection with four allegations including of rape and molestation.

Gemma Lindfield, for the Swedish prosecutors, said the first involved complainant A, who said she was the victim of "unlawful coercion" on the night of 14 August in Stockholm. The court heard Assange is accused of using his body weight to hold her down in a sexual manner.

The second charge alleged Assange "sexually molested" Miss A by having sex with her without a condom when it was her "express wish" one should be used.

The third charge claimed Assange "deliberately molested" Miss A on 18 August "in a way designed to violate her sexual integrity". The fourth charge accused Assange of having sex with a second woman, Miss W, on 17 August without a condom while she was asleep at her Stockholm home.

Lindfield argued there was a "high risk of flight" because of Assange's "lifestyle, connections and potential assets".

He had access to funds, through PayPal donations to the WikiLeaks website, had a "network of international contacts", lived a "nomadic" lifestyle, and spent his time in "hiding", she said. The court later heard that for the past three weeks he had been staying at a UK address, and before then had spent two months living at the Frontline media club in Paddington.

There was no record of him entering the UK in the first place. He had displayed an unwillingness to co-operate, refusing to be photographed, fingerprinted or give a DNA sample on arrest, she added.

No details were given about the strength of evidence, with Lindfield saying it "is not a factor in relation to bail". She also opposed bail for reasons of his personal safety, saying if granted "any number of unstable persons could take it upon themselves to cause him serious harm".

"This is someone, simply put, to whom no conditions, even the most stringent conditions, could be imposed that would ensure he surrendered to the jurisdiction of this court," she said.

John Jones, lawyer for Assange, said the case must be "shorn of all political and media hysteria" associated with WikiLeaks. Assange was of previous good character, and had voluntarily handed himself in to Kentish Town police station in London. His refusal to be photographed, fingerprinted or give a DNA sample was on legal advice.

He had stayed in Sweden for 40 days after the allegations were made to answer the charges and only left the country after being given "express permission" by the Swedish prosecutor.

Since he arrived in the UK he had "consistently agreed to talk to the Swedish authorities". His defence fund had been frozen, and he would be "instantly recognised" if he tried to leave the country, said Jones. "He resists extradition as it is disproportionate to extradite someone under these circumstances. There has been every indication that the point of this warrant is to get him back for questioning."

The judge said the warrant did state it was for prosecution.

Others offering surety were Professor Patricia David, and the lawyer Geoffrey Sheen, president of Union Solidarity International, who both said although they did not know Assange they were concerned about human rights. An unnamed relative of Assange offered £80,000.

But Judge Riddle said: "The nature and strength of the evidence is not there, this is normal at this stage in proceedings. What we have here is the serious possible allegations against someone with comparatively weak community ties in this country. He has the means and ability to abscond if he wants to and I am satisfied that there are substantial grounds to believe if I granted him bail he would fail to surrender."

Downing Street said Assange's arrest was "a matter for the police" and there had been no ministerial involvement.

Unlike the UK, Swedish rape law is not based on consent but on the aforementioned concept of sexual integrity. There are a number of possible offences against this integrity. Those that involve both penetration and either physical force or a threat of some illegal act, such as violence, are classified as rape. So are assaults on people who are helpless at the time, either as a result of intoxication or severe mental disturbance. The degree of physical force involved need only be very small. It can be enough merely to move the victim's legs apart, according to Gunilla Berglund, at the Swedish ministry of justice. Rape carries a sentence of between two and six years; aggravated rape a sentence of four to 10 years.

An issue concerning Assange's lawyers is the lack of bail in Swedish criminal procedure. Suspects are remanded in custody when legal grounds can be made out for their detention – particularly when they are foreigners who are deemed at risk of absconding. But there are strict limits on the timescale for bringing a suspect to trial, with a formal charge required within two weeks of being remanded into custody, and trial one week after that. The Swedish director of public prosecutions, Marianne Ny, dismissed suggestions of a political motive for the rape allegations.