(CNN) -- British intelligence hasn't broken any laws in sharing data with its American counterparts in counterterrorism efforts, Foreign Secretary William Hague said Sunday.
"The idea that in GCHQ people (British intelligence) are sitting working out how to circumvent a UK law with another agency in another country is fanciful," Hague told the BBC, referring to Britain's communications intelligence agency. "It is nonsense, and I think that I can give people that assurance." GCHQ is the acronym for Government Communications Headquarters, a British intelligence agency.
Hague spoke after a week of revelations about the scale of data-gathering by GCHQ's U.S. counterpart, the National Security Agency. Britain's the Guardian reported Saturday that GCHQ had access to an American data-mining system known as PRISM, suggesting it could "circumvent the formal legal process" required to seek personal data under British law.
Hague didn't confirm or deny whether British intelligence received information from the American programs. But the United States and Britain have shared intelligence since World War II, and Hague said British law "provides for intelligence-gathering that is authorized, necessary, proportionate and targeted -- targeted on what we really need to know."
"The net effect is that if you are a law-abiding citizen of this country, going about your business and your personal life, you have nothing to fear -- nothing to fear about the British state or intelligence agencies listening to the contents of your phone calls or anything like that," he said. "Indeed, you'll never be aware of all the things those agencies are doing to stop your identity being stolen and to stop a terrorist blowing you up tomorrow.
"But if you are a would-be terrorist or the center of a criminal network or a foreign intelligence agency trying to spy on Britain, you should be worried, because that is what we work on," he continued. "And we are, on the whole, quite good at it."
Wednesday, the Guardian disclosed a secret order from a U.S. intelligence court that required Verizon Business Network Services to give telephone records detailing the time, location and telephone numbers involved in domestic calls from April 25 to July 19. Thursday, the Washington Post and the Guardian disclosed the existence of PRISM, reporting that the program allows NSA analysts to extract details of customer activities -- including "audio and video chats, photographs, e-mails, documents" and other materials -- from computers at Microsoft, Google, Apple and other Internet firms.
In the wake of the revelations, the U.S. government declassified some details of the programs and defended the programs as both legal and valuable to heading off the threat of terrorism. Director of National Intelligence James Clapper said Saturday the surveillance programs are "conducted under authorities widely known and discussed, and fully debated and authorized by Congress."
"In a rush to publish, media outlets have not given the full context -- including the extent to which these programs are overseen by all three branches of government," Clapper said.
U.S. officials said earlier that phone-call data isn't looked at unless investigators sense a tie to terror, and only then on the authority of a judge. Officials say analysts are forbidden from collecting the Internet activity of American citizens or residents, even when they travel overseas. And President Barack Obama tried to reassure Americans about the programs Friday, saying, "Nobody is listening to your telephone calls."
Clapper's office called PRISM "an internal government computer system used to facilitate the government's statutorily authorized collection of foreign intelligence information from electronic communication service providers under court supervision." It was created in 2008, targets "foreign targets located outside the United States" and gets reviewed by the administration, Congress and judges.
"There is not a target on Americans," Rep. Mike Rogers, the chairman of the House Intelligence Committee, told reporters Sunday.
"There has to be a non-U.S. person believed to be on foreign soil. That is a huge difference than what is being portrayed in the media," said Rogers, R-Michigan.
But Colorado Democratic Sen. Mark Udall, who's long called for greater transparency in how the government collects data on Americans, said the legal authority should be reopened for debate after last week's disclosures.
"Maybe Americans think this is OK, but I think the line has been drawn too far towards 'We're going to invade your privacy,' versus 'We're going to respect your privacy,' " Udall told CNN's "State of the Union."
Udall is a member of the Senate Intelligence Committee. He and Sen. Ron Wyden, D-Oregon, have criticized the scope of the classified programs that allow the collection of Americans' phone records -- but have been limited in what they could say publicly.
Udall told CNN that claims that the monitoring has thwarted terrorist attacks are overblown.
"It's unclear to me we've developed any intelligence through the metadata program that's led to the disruption of plots that could have been attained through other means," Udall said, pushing back on assertions by both administration officials and Republican Intelligence Chairman Mike Rogers that a specific plot was stopped using the massive collection of phone records.
CNN's Kevin Liptak contributed to this report.