As Congress debates whether to permanently ban a counterterrorism surveillance program, a privacy watchdog this week revealed that the now-dormant program cost $100 million and led to one investigation in four years.

The National Security Agency’s collection of call-detail records was “expensive, plagued with data integrity concerns, and produced minimal intelligence relative to other national security programs,” two Republican members of the Privacy and Civil Liberties Oversight Board, an independent executive-branch watchdog, said in a report issued Wednesday.

A Democratic member, Travis LeBlanc, joined his GOP colleagues, Jane Nitze and Aditya Bamzai, in the board’s unanimous assessment. “The inescapable conclusion is that the program was a $100 million waste,” LeBlanc said in a separate statement.

The report comes as Congress grapples with a related but far more contentious issue — how extensively to strengthen privacy protections in the Foreign Intelligence Surveillance Act, which allowed the NSA record collection and authorizes the government to undertake wiretaps and searches in counterterrorism and espionage investigations.

The watchdog report did not state what results, if any, the lone investigation produced. But even the NSA panned the program’s yield, saying that 15 intelligence reports derived from the data over almost four years was an “extremely low” figure, according to the privacy board.

This was the board’s first public oversight report since it was reactivated in October 2018. The five-member group pushed hard to get even these few details declassified, Chairman Adam Klein said. But the group had hoped for more.

“Unfortunately,” then-acting director of national intelligence Joseph Maguire “did not agree,” Klein said. “My view is that it would have been appropriate for the DNI to provide additional transparency.”

Launched in its current form in 2015, the NSA call-records program grew out of a post-9/11 effort to detect foreign terrorist plots against the United States by finding clues in phone-call patterns. Initially it involved the agency gathering hundreds of millions of records each day from major phone companies to be able to sift through them for calls linked to a suspect’s phone number.

Responding to public outrage over the program’s scope, revealed in a 2013 leak by NSA contractor Edward Snowden, Congress scaled back the collection in 2015 by passing the USA Freedom Act.

That law, which expires March 15, requires the NSA to obtain records from the phone companies that are linked to a suspect’s phone number instead of amassing the records in a database of its own. The agency gets information such as who called whom, when and for how long, among other details. But no content is provided.

Nonetheless, the phone companies sometimes misstepped, providing incorrect data that the NSA had no authority to collect from 2017 to 2019, the report stated.

In early 2019, the NSA suspended the program, having concluded that it was of limited value given the cost and compliance issues. The House Judiciary Committee this week introduced a bill to reauthorize the USA Freedom Act that included a measure to shutter the program for good. There is broad support across Congress for such a move. The White House, however, would like to see the authority preserved in case one day the NSA wishes to revive the collection.

Meanwhile on Wednesday, the committee put off a vote on a bill to reauthorize the USA Freedom Act amid disagreements over proposed amendments. A particularly contentious measure introduced by Rep. Zoe Lofgren (D-Calif.) deals with court-appointed “amicus curiae,” or special advocates to the Foreign Intelligence Surveillance Court, which hears government surveillance applications in secret. Her measure would permit the advocates to have access to the classified application and any supporting data after a judge has approved it.