The Guardian has come under concerted pressure and intimidation designed to stop it from publishing stories of huge public interest that have revealed the "staggering" scale of Britain's and America's secret surveillance programmes, the editor-in-chief of the newspaper has said.

Giving evidence to a parliamentary committee about stories based on the National Security Agency leaks from the whistleblower Edward Snowden, Alan Rusbridger said the Guardian "would not be put off by intimidation, but nor are we going to behave recklessly".

He told MPs that disclosures from the files had generated a global debate about the powers of state agencies, and the weaknesses of the laws and oversight regimes they worked within.

"In terms of the broader debate, I can't think of a story in recent times that has ricocheted around the world like this has and which has been more broadly debated in parliaments, in courts and amongst NGOs," he said.

"The roll call of people who have said there needs to be a debate about this includes three presidents of the United States, two vice-presidents, generals, the security chiefs in the US [who] are all saying this is a debate that in retrospect we had to have."

During an hour-long session in front of the home affairs select committee, Rusbridger also:

• Said the Guardian had consulted government officials and intelligence agencies – including the FBI, GCHQ, the White House and the Cabinet Office – on more than 100 occasions before the publication of stories.

• Said the D-Notice committee, which flags the potential damage a story might cause to national security, had said that nothing published by the Guardian had put British lives at risk.

• Argued that news organisations that had published stories from the Snowden files had performed a public service and highlighted the weakness of the scrutiny of agencies such as GCHQ and the NSA. "It's self-evident," he said. "If the president of the US calls a review of everything to do with this and that information only came to light via newspapers, then newspapers have done something oversight failed to do."

• Asked why parliament had not demanded to know how 850,000 people had been given access to the GCHQ top-secret files taken by Snowden, who was a private security contractor.

Rusbridger said the Guardian had been put under the kind of pressure to stop publishing stories that would have been inconceivable in other countries.

"They include prior restraint, they include a senior Whitehall official coming to see me to say: 'There has been enough debate now'. They include asking for the destruction of our disks. They include MPs calling for the police to prosecute the editor. So there are things that are inconceivable in the US.

"I feel that some of this activity has been designed to intimidate the Guardian."

In one curious exchange, the committee chair, Keith Vaz, asked Rusbridger if he loved his country.

"I'm slightly surprised to be asked the question," replied Rusbridger. "But, yes, we are patriots and one of the things we are patriotic about is the nature of democracy, the nature of a free press and the fact that one can in this country discuss and report these things.

"One of the things I love about this country is that we have that freedom to write, and report, and to think and we have some privacy, and those are the concerns which need to be balanced against national security, which no one is underestimating. I can speak for the entire Guardian staff who live in this country that they want to be secure too."

At one point, the MP Mark Reckless suggested a criminal offence had been committed by sharing some of the Snowden material with the New York Times.

"You have I think Mr Rusbridger admitted a criminal offence in your response. Do you consider that it would not be in the public interest for the CPS [Crown Prosecution Service] to prosecute?"

Rusbridger replied: "I think it depends on your view of a free press."

He said the Guardian had not lost control of any of the documents and the newspaper had used "military-grade" encryption to safeguard the files.

"No data was lost, we lost control of no data. No names have leaked from the Guardian."

There was a testy set of exchanges between the editor and Michael Ellis.

The Tory MP asked Rusbridger about stories in the Guardian that revealed GCHQ had a Pride group. Ellis claimed this had endangered the security of GCHQ staff. "You've lost me," said Rusbridger. He said the details of the existence of the Pride group were publicly available on the internet.

The Guardian has published a series of stories about the mass surveillance techniques of GCHQ and its US counterpart, the NSA, over the last six months; two of the most significant programmes uncovered in the Snowden files were Prism, run by the NSA, and Tempora, which was set up by GCHQ. Between them, they allow the agencies to harvest, store and analyse data about millions of phone calls, emails and search-engine queries.

Rusbridger's answers referred to comments made to a parliamentary committee last month by the chiefs of Britain's three intelligence agencies – Sir Iain Lobban, the director of GCHQ, Andrew Parker, the director general of MI5, and Sir John Sawers, chief of MI6. The men had claimed that the Snowden revelations had damaged national security and that terrorists were likely rubbing their hands in glee.

Asked about this, Rusbridger said: "It is important context that the editors of probably the world's leading newspapers … took virtually identical decisions. This is not a rogue newspaper. It is serious newspapers that have long experience of dealing with national security.

"The problem with these accusations is they tend to be very vague and not rooted in specific stories."

Rusbridger then quoted senior officials from the UK and the US who "have told me personally that there has been no damage. A member of the Senate intelligence committee said to us: 'I have been incredibly impressed by what you have done … I have seen nothing that you have done that has caused damage."

Nick Pickles, director of Big Brother Watch, said: "Newspapers around the world, from the Guardian to the Washington Post and Der Spiegel, have done what our own parliamentary oversight committee and other oversight bodies failed to do: they exposed unprecedented surveillance being undertaken without the knowledge or approval of our elected representatives.

"Spies spy, but they should not be able to write their own rules, exploiting woefully out-of-date legislation to collect information on millions of innocent people.

"If the three intelligence chiefs had previously faced anywhere near as rigorous cross-examination then perhaps we would not have been so dependent on the Guardian and other newspapers to learn just how out of control surveillance had become."

Earlier today, the Watergate journalist and author, Carl Bernstein, wrote an open letter in which he said Rusbridger's appearance at the committee was "dangerously pernicious".

Bernstein said it was an attempt by the "highest UK authorities to shift the issue from government policies and excessive government secrecy in the United States and Great Britain to the conduct of the press".

"You are being called to testify at a moment when governments in Washington and London seem intent on erecting the most serious (and self-serving) barriers against legitimate news reporting – especially of excessive government secrecy – we have seen in decades," Bernstein wrote.

Yesterday the UN special raporteur on counter-terrorism and human rights, Ben Emmerson, announced he was launching an investigation into the surveillance programmes operated by GCHQ and the NSA.

He said the Guardian and other media organisations reporting the Snowden revelations had disclosed matters of genuine public interest and concern to states across the globe.

"The astonishing suggestion that this sort of journalism can be equated with aiding and abetting terrorism needs to be scotched decisively," Emmerson said. "Attacking the Guardian is an attempt to do the bidding of the services themselves, by distracting attention from the real issues."