LONDON - The Guardian newspaper says the British government forced it to destroy files or face a court battle over its publication of US security secrets leaked by Edward Snowden, as the fallout over the arrest of a man linked to the fugitive intensifies.
The claim by the paper's editor Alan Rusbridger came as Britain faced a second day of questions over why the partner of US journalist Glenn Greenwald had been detained and questioned at a London airport for nine hours.
David Miranda has been working with Greenwald and The Guardian on publishing material leaked by Snowden, the former US National Security Agency (NSA) worker who has turned leaker.
In response to growing criticism of the detention, Britain's Home Office interior ministry said police had been looking for "stolen information" that could be of use to terrorists when they had stopped Miranda.
Without mentioning him by name, a Home Office spokeswoman said: "If the police believe that an individual is in possession of highly sensitive stolen information that would help terrorism, then they should act and the law provides them with a framework to do that.
"Those who oppose this sort of action need to think about what they are condoning."
Writing in Tuesday's edition of The Guardian, Rusbridger said that two months ago he had been contacted by "a very senior government official claiming to represent the views of the prime minister".
The call led to two meetings in which "he demanded the return or destruction of all the material we were working on".
At the time, the paper was in the middle of publishing candid revelations about mass surveillance programmes conducted by the NSA and its British counterpart, GCHQ, after Snowden handed them thousands of documents.
Rusbridger claimed that in a call "from the centre of government", someone he does not identify told him: "You've had your fun. Now we want the stuff back."
"There followed further meetings with shadowy Whitehall figures," he continued. "The demand was the same: 'hand the Snowden material back or destroy it... You've had your debate. There's no need to write any more'."
The editor said the government threatened to use the courts to try and obtain the leaked documents if the paper did not destroy them themselves.
"And so one of the more bizarre moments in The Guardian's long history occurred," he added.
"With two GCHQ security experts overseeing the destruction of hard drives in The Guardian's basement just to make sure there was nothing in the mangled bits of metal which could possibly be of any interest to passing Chinese agents."
Rusbridger gave no explanation of why he had waited a month to reveal the destruction of the computer equipment.
In his article, he said the detention of Miranda was a worrying development and showed "it may not be long before it will be impossible for journalists to have confidential sources".
Miranda said Monday that he had been stopped at London's Heathrow Airport on the way to Brazil from Berlin where he had been visiting a filmmaker.
He claims he was questioned about "my whole life" by six agents and had his computer and memory cards confiscated.
A furious Greenwald said Monday that his boyfriend had been the subject of "a clear attempt at intimidation" and he vowed to train his sights on Britain and its intelligence services in future.
The White House said it had been informed that Britain was about to arrest Greenwald's partner but denied it had requested the action.
"There was a heads-up that was provided by the British government, so this is something we had an indication was likely to occur," White House deputy spokesman Josh Earnest told reporters.
"But it's not something that we requested, and it's something that was done specifically by the British law enforcement officials."
The Guardian was one of the original media partners of WikiLeaks and its founder Julian Assange, and helped to publish material from the mass of confidential cables leaked by US military worker Bradley Manning.
However the newspaper later fell out with Assange.
Snowden has been granted asylum in Russia after fleeing to Moscow, despite US demands that he be returned to face trial on charges including espionage.