An independent federal privacy watchdog has concluded that the National Security Agency's program to collect bulk phone call records has provided only minimal" benefits in counterterrorism efforts, is illegal and should be shut down. The findings are laid out in a 238-page report [that represents] the first major public statement by the Privacy and Civil Liberties Oversight Board, which Congress made an independent agency in 2007 and only recently became fully operational. The Obama administration has portrayed the bulk collection program as useful and lawful. But in its report, the board lays out what may be the most detailed critique of the government's once-secret legal theory behind the program: that a law known as Section 215 of the Patriot Act, which allows the F.B.I. to obtain business records deemed "relevant" to an investigation, can be legitimately interpreted as authorizing the N.S.A. to collect all calling records in the country. The program "lacks a viable legal foundation under Section 215, implicates constitutional concerns under the First and Fourth Amendments, raises serious threats to privacy and civil liberties as a policy matter, and has shown only limited value," the report said. "As a result, the board recommends that the government end the program." The report also sheds light on the history of the once-secret bulk collection program. It contains the first official acknowledgment that the Foreign Intelligence Surveillance Court produced no judicial opinion detailing its legal rationale for the program until last August, even though it had been issuing orders to phone companies for the records and to the N.S.A. for how it could handle them since May 2006.