“Mr. Miranda does not accept the assertions they have made,” she added, “and is disappointed that the U.K. government is attempting to justify the use of terrorist powers by making what appear to be unfounded assertions.”

Mr. Rusbridger called Mr. Robbins’s assertions inaccurate and asked why, if the material made public by Mr. Snowden presented such acute danger to national security, the government had done so little before detaining Mr. Miranda.

“The way the government has behaved over the past three months belies the picture of urgency and crisis they have painted,” he wrote on The Guardian’s Web site. “The government claims that they have at all times acted with the utmost urgency because of what they believed to be a grave threat to national security. However, their behavior since early June — when The Guardian’s first Snowden articles were published — belies these claims.”

To give an example of what he views as the British government’s lack of urgency, Mr. Rusbridger said in a statement that in late July The Guardian told the British authorities that some of the classified material it received from Mr. Snowden had been sent to The New York Times and ProPublica. This took place, he said, two days after The Guardian destroyed copies of documents provided by Mr. Snowden because the newspaper was facing threats of legal action by the British government.

Mr. Rusbridger said weeks had passed before the British government contacted The Times. “We understand the British Embassy in Washington met with The New York Times in mid-August — over three weeks after The Guardian’s material was destroyed in London,” he said. “To date, no one has contacted ProPublica, and there has been two weeks of further silence towards The New York Times from the government.”

A Times spokeswoman, Eileen Murphy, said, “Jill Abramson and Dean Baquet met with a British government representative in Washington.” Ms. Abramson is the executive editor of The Times, and Mr. Baquet is the managing editor.

“At the meeting, The New York Times was asked to relinquish classified material, a request that was declined,” Ms. Murphy said.Under the interim injunction issued by the high court, investigators will be permitted to determine whether possessing the encrypted files could constitute a crime of “communication of material to an enemy” or a crime of communicating material about members of the military and the intelligence agencies that might prove useful for terrorists.

The case will receive a full judicial review in late October.