Miranda detention is internal matter for UK, EU says

But she added: "I would doubt the commission has any comments to make on the application of national security legislation."

Her comments come after David Miranda, a Brazilian national who is the partner of Guardian journalist Glenn Greenwald, was taken into custody at Heathrow airport’s transit area on Sunday.

He was held for nine hours and British security officials made threats to incarcerate him if he refused to co-operate.

The Guardian says he was ferrying documents between US film-maker Laura Poitras and Greenwald, both of whom are working on US security documents leaked by Edward Snowden.

Heathrow agents confiscated Miranda’s computer, mobile phone, camera, a game console, and memory sticks.

He was detained under the so-called schedule 7 of the Terrorism Act 2000 that allows police to question anyone up to nine hours in a transit area.

The act strips away the normal protections for suspects and journalists.

His detention and treatment has since drawn widespread condemnation from international and national observers, prompting the UK’s anti-terrorism legislation watchdog to call for an overhaul of the law.

A former British lord chancellor, Lord Falconer of Thoroton, who helped introduce the anti-terror legislation used to detain Miranda, told the Guardian that the police had no right to detain him under the act.

"What schedule 7 allows an examining officer to do is to question somebody in order to determine whether he is somebody who is preparing, instigating or commissioning terrorism. Plainly, Mr Miranda is not such a person," he said.

For its part, Downing Street says it is a police matter, while UK home secretary Theresa May said police acted within the law.

Meanwhile, the White House distanced itself from Downing Street after UK agents forced the Guardian’s London office to destroy documents leaked by Snowden.

The paper’s editor, Alan Rusbridger, said two British security officials in July oversaw the destruction of hard drives containing the leaked files.

Rusbridger called it a "pointless piece of symbolism that understood nothing about the digital age," because the files had already been copied and distributed elsewhere.

The White House on Tuesday said it could not imagine itself taking part in such a scenario, even to protect national security.