LONDON -- Stung by allegations that it colluded with American intelligence agencies to collect data on its citizens, Britain's government insisted Monday that its secret services operate within the law but did not give details of what rules apply to some requests for information from foreign powers.
Despite the growing controversy over the issue, the British government has yet to confirm or deny reports that it had been given information from an American surveillance program called Prism, which is said to have collected Internet data on foreigners abroad from companies including Google, Facebook, Microsoft, Apple, Yahoo and Skype.
But in a statement to Parliament the Foreign Secretary, William Hague, rejected as "baseless" suggestion that the intelligence-gathering facility, Government Communications Headquarters, known as GCHQ, had used its partnership with the United States to secure information not legally available to it at home.
Britain, he added, had "one of the strongest systems of checks and balances and democratic accountability for secret intelligence anywhere in the world."
"To intercept the content of any individual's communications in the U.K. requires a warrant signed personally by me, the home secretary or another secretary of state," he said. "This is no casual process."
However, the Prism program gathers metadata -- information about patterns and locations of communications -- rather than content.
Asked by Douglas Alexander, spokesman for foreign affairs from the opposition Labour Party, what controls apply over requests from GCHQ for information based on searches of foreign databases -- rather than intercepts -- Mr. Hague sidestepped.
"Because circumstances vary and because procedures vary according to the situation, I don't want to give a categoric answer," Mr. Hague told British lawmakers, though he added that "ministerial oversight, independent scrutiny is there."
"The idea that operations are carried without ministerial oversight, somehow getting around U.K. law, is a mistaken idea," Mr. Hague added.
Mr. Alexander praised the work of the intelligence services but called for reassurances "in recognition of the depth of public concern that has arisen in recent days."
Last week, The Guardian newspaper reported that GCHQ generated 197 intelligence reports through the system in the year to May 2012. GCHQ has refused to comment on the details of the claims but said in a statement that its work "is carried out in accordance with a strict legal and policy framework which ensures that our activities are authorized, necessary and proportionate, and that there is rigorous oversight."
According to experts, the legal situation remains opaque. "We are told this is lawful but the precise nature of these legal judgments are hidden from us," said Richard Aldrich, a professor of international security at the University of Warwick. He argued that intelligence agencies now had access to enormous stores of information that could be cross-checked with other data to build up a profile of individuals' lives.
"The last 10 years has been about working out how to warehouse unbelievable amounts of boring data and how to analyze that data -- and they have cracked it," Mr. Aldrich said. Through such a process it would be possible for the authorities "to have a better memory of what I was doing 10 months ago than I have," he said.
Politicians in continental Europe also expressed concerns. "All our emails and other electronic communication, including social media, even if sent only between European Union citizens, can be intercepted and read by U.S. security services," said Guy Verhofstadt, a former Belgian prime minister who leads the Alliance of Liberals and Democrats in the European Parliament. "This has obvious and very serious privacy consequences for E.U. citizens."
Earlier Monday Prime Minister David Cameron spoke in defense of the British intelligence agencies, also insisting they were operating within the law.
"I see every day the vital work they do to keep us safe," he said while answering questions after a speech in Essex, "but it is vital work that is done under a legal framework within the law and subject to proper scrutiny by the intelligence and security committee."
"The intelligence services operate within the law, within the law that we have laid down, and they are also subject to proper scrutiny by the intelligence and security committee of the House of Commons," he said.
Though he added that he was satisfied that British agencies operate in a proper way, Mr. Cameron also said that the government could not give a "running commentary" on intelligence issues.
This article originally appeared in The New York Times.