– An independent federal privacy watchdog has concluded that the NSA’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, scheduled for release by Thursday and obtained by the New York Times. It is the first major public statement by the Privacy and Civil Liberties Oversight Board, which Congress made an independent agency in 2007 and recently became fully operational.

The report is likely to inject a significant new voice into the debate over surveillance, underscoring that the issue was not settled by a high-profile speech given last week by President Obama.

Interpreting the Patriot Act

Obama consulted with the board and another review group. But while he said in his speech that he was tightening access to the data and declared his intention to find a way to end government collection of the bulk records, he said the program’s capabilities should be preserved.

The Obama administration has portrayed the bulk collection program as useful and lawful while at the same time acknowledging concerns about privacy and potential abuse. 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 FBI to obtain business records deemed “relevant” to an investigation, can be legitimately interpreted as authorizing the NSA 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.”

While a majority of the five-member board embraced that conclusion, two members dissented from the view that the program was illegal. But the panel was united in 10 other recommendations, including deleting raw phone records after three years instead of five and tightening access to search results.

The report also sheds light on the history of the 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 August, even though it had been issuing orders to phone companies for the records and to the NSA for how it could handle them since May 2006.

‘A reasonable reading’

The board’s legal critique of the program was approved by David Medine, the board’s chairman and a former Federal Trade Commission official in the Clinton administration; Patricia M. Wald, a retired federal appeals court judge named to the bench by President Jimmy Carter; and James X. Dempsey, a civil liberties advocate.

But the other two members — Rachel L. Brand and Elisebeth Collins Cook, both Justice Department lawyers in the George W. Bush administration — rejected the finding that the program was illegal.

They wrote in separate dissents that the board should have focused exclusively on policy and left legal analysis to the courts. Last month, two U.S. district judges reached opposite legal conclusions in separate lawsuits challenging the program.

Brand wrote that while the legal question was “difficult,” the government’s legal theory was “at least a reasonable reading, made in good faith by numerous officials in two administrations of different parties.” She worried that declaring that counterterrorism officials “have been operating this program unlawfully for years” could make agencies overly cautious in taking steps to protect the country.

But the board was unanimous in recommending a series of immediate changes. The three in the majority wanted those changes as part of a brief wind-down period, while the two in dissent wanted them to be structural for a program that would continue. Some recommendations dovetailed with Obama’s speech, including limiting analysts’ access to the call records of people no further than two links removed from a suspect, instead of three, and creating a panel of outside lawyers to serve as public advocates in major cases involving secret surveillance programs.