Two US senators have raised concerns that the Central Intelligence Agency (CIA) is again spying upon unwitting Americans.
The agency has “secretly” conducted warrantless surveillance through a newly disclosed programme, Senators Ron Wyden and Martin Heinrich alleged.
In a letter to intelligence officials, the two Democrats called for declassifying details of the programme.
Government data collection has been the subject of much controversy in the US.
Officially, the CIA and National Security Agency (NSA) have a foreign surveillance mission and domestic spying is prohibited by the CIA’s 1947 charter.
But in 2013, a programme of data collection using extensive internet and phone surveillance by American intelligence was disclosed to the public by Edward Snowden, a CIA contractor-turned whistle-blower.
A Washington Post analysis of the Snowden leak found some 90% of those being monitored were ordinary Americans “caught in a net the National Security Agency had cast for somebody else”.
Top officials had until then denied – and even lied under oath to Congress – that they were knowingly collecting such data.
The programme, known as Prism, was later ruled unlawful by a US court.
But a government watchdog last year disclosed two CIA data collection efforts that Senators Wyden and Heinrich now claim are likely to be again subjecting Americans to warrantless searches.
The CIA released a declassified report on one of the programmes on Thursday, but declined to declassify the other, citing the need to protect “sensitive tradecraft methods and operational sources”.
But Mr Wyden, of Oregon, and Mr Heinrich, of New Mexico, said by failing to do so the agency was “undermin[ing] democratic oversight and pos[ing] risks to the long-term credibility of the Intelligence Community”.
The senators, who sit on the Intelligence committee, said the public deserved to know “the nature and full extent” of the surveillance, which is all but certain to include records on Americans.
The still-classified programme operates under the authority of a Reagan-era executive order and is therefore “entirely outside the statutory framework that Congress and the public believe govern this collection,” they said.
The American Civil Liberties Union (ACLU) non-profit said: “These reports raise serious questions about what information of ours the CIA is vacuuming up in bulk and how the agency exploits that information to spy on Americans”.
“In the course of any lawful collection, CIA may incidentally acquire information about Americans who are in contact with foreign nationals,” a CIA spokesman told BBC News on Friday.
“When CIA acquires information about Americans, it safeguards that information in accordance with procedures,” set out to restrict how it can use the data, the spokesman added.