The photograph of two suspected Swiss secret policemen has been blamed for an FBI crackdown that closed 20 UK-based news websites.

Now the British Government has been accused of helping to create an “information Guantanamo” after secret powers were used to confiscate computer servers used by the sites.

The servers, held in London for Indymedia, an independent collective of journalists, were handed over by web-hosting company Rackspace following an order served by the FBI. The company says it is barred by the terms of a gagging order from saying anything else. And it has refused to even tell its customers — Indymedia — why the websites were shut down and whom the servers were handed to.

The Nantes Indymedia site last month posted photos of who it believed to be undercover Swiss police officers photographing protesters at a French event.

Indymedia received a request from the FBI to pull those photos as they “revealed personal information” about the undercover police, said Indymedia press officer Hep Sano.

The Nantes site was one of 20 hosted by Rackspace in London.

The Home Office has refused to confirm or deny that the seizure of the servers took place.

In a statement Rackspace said it was complying with a court order issued under the Mutual Legal Assistance Treaty, which establishes procedures for countries to assist each other in investigations such as international terrorism, kidnapping and money laundering.

The FBI has confirmed that it issued a subpoena to Rackspace “on behalf of a third country”.

Indymedia was established in 1999 to cover theWorld Trade Organisation protests in Seattle and consists of thousands of journalists worldwide contributing to 140 news websites.

According to Indymedia, the order to seize the computers may have come to the FBI via the Swiss authorities using the MLAT treaty.

A British Indymedia journalist, who asked not to be named, said: “The first thing people knew about this was when the servers suddenly stopped responding on Thursday. People started calling Rackspace and they did not have much information to give out at all. The servers have disappeared into a sort of information Guantanomo Bay.”

The UK version of Indymedia has a back-up version and is now online again. But according to the group, 1,000 hours of audio footage have been lost and up to two years of archived articles. Some of the downed sites were not backed-up.

International Federation of Journalists general secretary Aidan White said: “We have witnessed an intolerable and intrusive international police operation against a network specialising in independent journalism.”

NUJ general secretary Jeremy Dear said: “To take away a server is like taking away a broadcaster’s transmitter. It is simply incredible that American security agents can just walk into a London office and remove equipment.

“In this nightmare world they can apparently close the operation down without any reason being given, without any chance to question or protest.”

MPs in the NUJ’s Parliamentary group plan to table questions to Home Secretary David Blunkett.

The union is also consulting lawyers on behalf of members whose work was affected by the seizure.

There are understood to be more than 100 regular contributors to Indymedia based in the UK.