Parliament’s Intelligence and Security Committee (ISC) said the interception did not amount to “indiscriminate surveillance,” but called for greater transparency from the security services.
Britain’s eavesdropping agency GCHQ and the US National Security Agency were at the centre of a storm in 2013 over the extent of their snooping following leaks from former US intelligence contractor Snowden.
GCHQ uses bulk interception to uncover threats by finding patterns and associations to trigger leads, a tactic that the report said was a crucial and appropriate first step.
Analysts can only examine individual communications on the authorisation of a government minister, and committee member Hazel Blears said “only a very tiny percentage of those collected are ever seen by human eyes.”
This amounted to thousands of items a day, according to the report, in which the exact number was redacted out.
It said the items read included “only the ones considered to be of the highest intelligence value.”
“Given the extent of targeting and filtering involved, it is evident that while GCHQ’s bulk interception capability may involve large numbers of emails, it does not equate to blanket surveillance, nor does it equate to indiscriminate surveillance,” Blears said.
“GCHQ is not collecting or reading everyone’s emails: they do not have the legal authority, the resources, or the technical capability to do so.”
The committee found that the intelligence agencies did not seek to circumvent the law, but Blears said the legal framework was “unnecessarily complicated and — crucially — lacks transparency.”
The report recommended that the tangle of current laws on intrusion be replaced by a new, single piece of legislation.
The report also found each spy agency had disciplined or sacked staff for inappropriately accessing personal information held in the datasets.
Spies who abuse their position should face a specific criminal offence, the report said.
Prime Minister David Cameron said: “We will consider the ISC’s findings and recommendations carefully.”
Meanwhile a watchdog warned that police forces have abused surveillance powers to snoop on their own officers’ phone records as part of relatively minor disciplinary investigations.
In a damning indictment, Interception of Communications Commissioner Anthony May said “an excessively high number” of such applications were unjustified.
“The applications often relied upon vague and dubious descriptions under the ‘umbrella’ of misconduct in public office,” he said.
Some of the applications centred on cases where officers were suspected of forming inappropriate relationships with victims of crime.
Elsewhere, Home Secretary Theresa May, the interior minister, has launched a judge-led inquiry into undercover policing, reviewing practices and making recommendations.
It follows revelations that police spied upon the family of murdered black teenager Stephen Lawrence and covertly collected information on justice campaign groups.
Undercover officers have even had sexual relationships and fathered children with campaigners under their false identities.