LONDON (AFP) - Foreign Secretary William Hague insisted on Monday that British spies have not used US surveillance programmes to get around laws restricting their ability to eavesdrop on the public.
Mr Hague, who cancelled a trip to Washington to address parliament on the issue, said Britain's electronic eavesdropping agency GCHQ operated within a strict legal framework.
"It has been suggested that GCHQ uses our partnership with the United States to get around UK law, obtaining information that they cannot legally obtain in the United Kingdom," Mr Hague said. "I wish to be absolutely clear that this accusation is baseless."
The Guardian newspaper, which along with The Washington Post revealed details last week of two vast electronic surveillance programmes operated by the US National Security Agency (NSA), reported that GHCQ has had access to the Internet-monitoring scheme PRISM since at least June 2010.
Seeking to calm public concern, Mr Hague told lawmakers that every time GCHQ wants to intercept an individual's communications the agency must seek a warrant signed by him, the interior minister or another secretary of state.
"This is no casual process," Mr Hague said.
"Every decision is based on extensive legal and policy advice. Warrants are legally required to be necessary, proportionate and carefully targeted." He added: "We take great care to balance individual privacy with our duty to safeguard the public and the UK's national security."
Mr Hague said that since the 1940s, the NSA and its forerunners have had a relationship with GCHQ that is "unique in the world".
This relationship "has stopped many terrorist and espionage plots against this country and it has saved many lives," he said.
"The growing and diffuse nature of threats from terrorists, criminals or espionage has only increased the importance of our intelligence relationship with the United States."
But asked by an opposition spokesman if it was possible that GCHQ has made mistakes and spied on innocent members of the public, Mr Hague admitted: "Everyone is capable of error... there will always be ways of improving our procedures."
He insisted that the rules surrounding surveillance "minimise the chance of error" and praised GCHQ for its "professionalism, dedication and integrity".
Parliament's Intelligence and Security Committee scrutiny panel, which is investigating possible use of the US schemes by GCHQ, was on Monday travelling to Washington on a long-planned trip.
Hague deplored the leak of the surveillance programmes by a former CIA employee, saying they had made the work of protecting national security in the United States and beyond more difficult.
Edward Snowden, 29, while he was a government contractor at the NSA, said his conscience drove him to reveal the scale of the monitoring of Internet users.