The US National Security Agency is set to overhaul the system it uses to store and manage secret data, in the wake of the international leaks from fugitive whistleblower Edward Snowden.

One of the country’s most senior defence officials said that the revelations that the agency was gathering millions of people’s phone records and intercepting internet communications represented “a failure to defend our own networks”.

Deputy Defence Secretary Ashton Carter said they would now have a “two-man rule” whereby system administrators like Mr Snowden would need to be accompanied by a colleague at all times when accessing sensitive intelligence.

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Previously the NSA’s chief, General Keith Alexander, said the former contractor was able to access so much information because the agency uses a single internal site designed to make sharing information easier.

And Mr Carter said: “There was an enormous amount of information concentrated in one place. That's a mistake. The loading of everything onto a server creates a risk.”

He said that in future the NSA would be much more careful about how it monitors its own workforce, and suggested that the Pentagon might bring in protocols similar to those used to keep tabs on intelligence officials at nuclear installations.

“When it comes to nuclear weapons, you watch people's behaviour in a special way. We don't let people all by themselves do anything,” he said. “There is always some aberrant individual and you've got to recognize that.”

The US government has claimed that Mr Snowden’s leaks have helped terrorists by making them aware of how their communications are intercepted.

Matthew Olsen, director of the National Counterterrorism Centre, confirmed during the forum that US intelligence indicates al-Qa'ida and related groups are seeking to change the way they work in order to avoid detection and surveillance.