LONDON (Reuters) - Britain on Monday dismissed as "baseless" accusations that security agencies had been circumventing British law by using information gathered on British citizens by Prism, a secret U.S. eavesdropping programme.
Prime Minister David Cameron's government has been under pressure from the opposition and the media to reassure the public after U.S. whistleblower Edward Snowden leaked details of Prism last week.
His disclosure lifted the lid on what he said was a vast surveillance system that stretched across the world, vacuuming up emails, electronic communications and phone data - including that of some Britons- that leaked documents showed was sometimes handed over to Britain's security services.
U.S. law imposes limits on the government's authority to snoop at home but virtually none on U.S. spies eavesdropping on the communications of foreigners, including in allied countries, such as Britain, with which Washington shares intelligence.
Foreign Secretary William Hague told parliament that Britain's own eavesdropping agency, GCHQ, always adhered to British law when processing such data.
"This accusation is baseless," he told parliament. "Any data obtained by us from the United States involving UK nationals is subject to proper UK statutory controls and safeguards."
The system amounted to "one of the strongest systems of checks and balances and democratic accountability for Secret Intelligence anywhere in the world", Hague said.
He would not confirm or deny any details of UK-U.S. intelligence sharing, saying that to do so could help Britain's enemies.
Cameron told reporters: "I'm satisfied that we have intelligence agencies that do a fantastically important job for this country to keep us safe, and they operate within the law."
Before and after a British soldier was hacked to death in London on May 22 in an incident the government described as a "terrorist" attack, there has been public debate in Britain about giving the security services more powers to eavesdrop.
Critics had suggested that PRISM gave GCHQ a "snoopers' charter by the back door" with Douglas Alexander, the Labour party's spokesman for foreign affairs, pushing the government to be more open on the subject.
Hague said Britain's parliamentary intelligence and security committee would receive a full report on PRISM on Tuesday and had already received "some information". By coincidence, its members are due in Washington on Monday to conduct talks with lawmakers and officials in the U.S. intelligence community.
"One of the big questions that's being asked is: If British intelligence agencies want to seek to know the content of emails, can they get round the normal law in the UK by simply asking an American agency to provide that information?" Malcolm Rifkind, the chairman of parliament's Intelligence and Security Committee, told BBC Radio 4.
"The law's actually quite clear: if the British intelligence agencies are seeking to know the content of emails about people living in the UK, then they actually have to get lawful authority," he said.
Britain's Guardian newspaper said it had obtained documents showing GCHQ had generated 197 intelligence reports from PRISM last year. It said GCHQ had been secretly gathering intelligence from PRISM and had had access to the system since at least June 2010.
Writing by Guy Faulconbridge, Michael Holden and Andrew Osborn; editing by Mark Heinrich