The National Security Agency’s program to bulk collect phone data breaks the law, violates civil liberties, does not make Americans more safe, and should be shut down, according to the federal government's own watchdog.

In a 238-page report obtained by the New York Times and Washington Post, the Privacy and Civil Liberties Oversight Board, which was created by Congress in 2007, issued the strongest rebuke of NSA spying yet from within the U.S. government.

The panel's decision, reported Thursday, takes direct aim at the legal argument cited to justify the mass phone data spying: Section 215 of the Patriot Act.

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,” reads the report, according to the New York Times.

“As a result, the board recommends that the government end the program.”

The panel also directly challenges the argument that spying is necessary to keep Americans safe from "terrorist" attacks—a justification echoed by intelligence circles and President Obama. The report states that it could find “no instance in which the program directly contributed to the discovery of a previously unknown terrorist plot or the disruption of a terrorist attack.”

“We believe that in only one instance over the past seven years has the program arguably contributed to the identification of an unknown terrorism suspect," the report states. "Even in that case, the suspect was not involved in planning a terrorist attack and there is reason to believe that the FBI may have discovered him without the contribution of the NSA’s program,” it found.

The ruling from the five person panel was not unanimous, with two members—who were both lawyers in the George W Bush-era Justice Department—dissenting.

Coming on the heals of Obama's widely criticized speech on NSA 'reforms,' the report amounts to a strong condemnation of the president's policies and is likely to bolster efforts to defend civil liberties against government spying.

"We welcome the board’s report, and we agree with is principal conclusions. The NSA’s call-records dragnet is illegal and ineffective and presents a serious threat to civil liberties," said American Civil Liberties Union Deputy Legal Director Jameel Jaffer. "The report should spur immediate action by both the administration and Congress."

"Let's not forget the legal rationale wasn't produced, and the PCLOB group itself hadn't even met until after Mr. Snowden's revelations," said Government Accountability Project (GAP) Executive Director Beatrice Edwards. "None of this would have happened if it weren't for his disclosures in June. We will continue to fight on his behalf to assert his rights as an American whistleblower."

_____________________