A report by the Privacy and Civil Liberties Oversight Board (PCLOB) has condemned the practices of the US National Security Agency and called for an end to its phone spying programme.
The members of the board claimed that there had not been one instance of phone surveillance that had been justified.
"We have not identified a single instance involving a threat to the United States in which the telephone records program made a concrete difference in the outcome of a counterterrorism investigation," the report stated, according to the Washington Post (opens in new tab).
"Moreover, we are aware of no instance in which the program directly contributed to the discovery of a previously unknown terrorist plot or the disruption of a terrorist attack."
Barack Obama was privy to the 238-page report before announcing curbs to the bulk collection of metadata by the NSA (opens in new tab) last week. However, the US president remained firm on the idea that NSA surveillance programmes were vital to national security, despite the report's claims.
"We shouldn't have to apologise just because our capabilities are greater than others," Obama said.
Related: Two year investigation launched into post-Snowden Internet (opens in new tab)
In contrast to Obama's announcement, the report argued that the statute upon which the spying is justified, "does not provide adequate basis to support this program".
"The Board believes that the Section 215 program has contributed only minimal value in combating terrorism beyond what the government already achieves through these and other alternative means," the report said.
"Cessation of the program would eliminate the privacy and civil liberties concerns associated with bulk collection without unduly hampering the government's efforts, while ensuring that any governmental requests for telephone calling records are tailored to the needs of specific investigations."