Watergate journalist Carl Bernstein backs Guardian handling of Edward Snowden leaks

Legendary Watergate journalist Carl Bernstein has written a letter of support to Guardian editor Alan Rusbridger, who is due to appear before MPs on Tuesday to face questions over his publication of intelligence files from US spy agency contractor Edward Snowden.

Bernstein, 69, said Rusbridger's appearance before the House of Commons Home Affairs Committee was a "dangerously pernicious" attempt by British authorities to shift the focus of the surveillance debate from excessive government secrecy in the United States and Britain to the conduct of the press. The Guardian was among several newspapers that published Snowden's leaks about Britain's GCHQ eavesdropping agency and its close cooperation with the US National Security Agency (NSA) in carrying out mass surveillance. Bernstein said the conduct of press had been admirable and responsible over the issue.

The articles published by the Guardian, the Washington Post and the New York Times based on Snowden's information were no help to terrorists or enemies of the nation, he added.

"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," he wrote in the letter, which was published on the Guardian website. "As we learned in the United States during our experience with the Pentagon Papers and Watergate, it is essential that no prior governmental restraints or intimidation be imposed on a truly free press," he said. "Otherwise, in such darkness, we encourage the risk of our democracies falling prey to despotism and demagoguery and even criminality by our elected leaders and government officials."

Bernstein's reporting, together with that of Washington Post colleague Bob Woodward, broke the Watergate scandal that eventually resulted in the resignation of US President Richard Nixon in 1974. He has since continued to focus on the theme of the use and abuse of power through books, magazine articles and television appearances.

The Snowden disclosures of mass surveillance by GCHQ and the NSA have embarrassed the British government and secret services, who argue the release of such sensitive information is a threat to national security. "They've put our operations at risk," John Sawers, the head of MI6, Britain's foreign intelligence service, told a parliamentary committee last month. "It's clear that our adversaries are rubbing their hands with glee - al Qaeda is lapping it up," he added. Rusbridger, a former Washington editor for the London Daily News, has defended the Guardian's role, saying it has provoked a debate about the extent of intelligence activities, which lawmakers had failed to do.