Pulitzer Prize-winning journalist Glenn Greenwald has said Europeans should defend their online privacy themselves rather than wait for Ireland to adopt a more robust approach to regulating Facebook.

A year after he began publishing material provided by Edward Snowden, exposing widespread US surveillance of global telecommunications, Greenwald said Irish politicians had little chance against large corporations such as Facebook, which he said were effectively operating outside democratic control.

"These companies have become so incredibly powerful . . . that we have a situation where even elected governments are almost no match and that poses a very serious problem," said Greenwald, speaking in Berlin, where he was promoting his book No Place to Hide.

"It is inconceivable to think of the Irish Government, the EU or US government imposing meaningful constraints on companies like Facebook and Google. "

Instead the most effective way of limiting digital surveillance, he said, was for people to think twice about using services “with a track record of supplying information to US intelligence”.

Another approach, he said, was for people to “build bricks” around their online activity by encrypting their digital communication.

Encrypting email and boycotting Facebook was, he said, “a more promising way of limiting their behaviour than hoping that some politicians in a capital somewhere will issue a regulation that does that”.

Greenwald's call comes ahead of a High Court ruling due on June 18th on whether Ireland's Data Protection Commissioner (DPC) was correct not to investigate Snowden's claims that Facebook International, based in Dublin and thus under Irish jurisdiction, supplied the NSA with European user data.

Greenwald said he met Snowden recently in Moscow and that he found the computer specialist essentially unchanged from the man he met for the first time a year ago in Hong Kong. “The fact he is not in a penal cage is a pretty good thing. He is free to participate in the debate he helped galvanise around the world,” said Greenwald.

He is free to move around in Moscow and is able to keep a low profile, the journalist said, because he looks “like an 18-year-old kid from Iowa ... on an exchange programme” rather than a world-famous whistleblower.

After months of revelations about high-level US spying in Germany, a Bundestag parliamentary inquiry has agreed to hear testimony from the ex-NSA contractor and has asked to meet him in Moscow for an "informal conversation" before deciding how to proceed.

While opposition parties and civil rights groups are demanding asylum for Snowden to allow him to testify in Berlin, the German government and their deputies sitting on the inquiry are opposed to this.

Greenwald has described their stance as “shameful”, arguing that German politicians had “not just a moral but a legal duty” to their voters to conduct a thorough investigation of the NSA claims by questioning Snowden in person.

The wrangling over testimony, Greenwald said, suggested German politicians remained “fearful of doing anything that might offend Washington”.

For his part, Snowden told Stern magazine that Berlin's hesitation might be because "German intelligence services are in bed with the Americans".

“Clearly facts continue to be kept secret which would cause outrage in public,” he said.

This week Germany’s attorney general opened a formal investigation into claims that the NSA tapped Chancellor Angela Merkel’s mobile phone, but said there was, so far, insufficient evidence for an investigation into claims of widespread data collection.

In Berlin, Greenwald promised to increase the pace of revelations from the Snowden files, a move he hopes will help boost awareness of the need for privacy in the digital age.

“Even though privacy is a difficult value to express and defend, the need for it is intuitive to all human beings,” he said.

On the first anniversary of his revelations, Snowden’s German lawyer confirmed this week that his client would apply to renew his asylum in Russia for another year.

The whistleblower, meanwhile, warned that unchecked collection and cross-referencing of digital data, from email messages to mobile phone mast signals, had made it easier than ever before to analyse, predict and influence human behaviour.

"By linking data and analysing it," he told Stern magazine, "I don't just know when you went to bed, I also know with whom."