U.S. intelligence officials have asked Congress to permanently extend a controversial program that has allowed the National Security Agency to collect millions of telephone records. Civil liberties groups aren’t happy about it.

In mid-August, outgoing Director of National Intelligence Dan Coats wrote leaders of two Senate committees to request that they extend authorization for the NSA to collect business records and U.S. residents’ phone records related to authorized national security investigations.

The NSA phone records collection program allowed the agency to collect so-called metadata, including the dates and senders of calls and texts, but not the content of those communications. Still, the NSA has reportedly collected billions of phone records since the program went into effect after the Sept. 11, 2001, terrorist attacks.

The NSA reportedly suspended the phone records collection program in late 2018 after the 2015 USA Freedom Act limited bulk collection of the data. The section of law authorizing the telephone records program expires in December.

But Coats argued that the intelligence community may need it in the future. “As our technology changes, our adversaries’ tradecraft and communications habits will continue to evolve and adapt,” he wrote. “In light of this dynamic environment, the Administration supports reauthorization of this provision.”

On the same day that Coats sent his letter, 37 civil and digital rights groups urged lawmakers to kill the “call detail records” (CDR) collection program in a letter to the House Judiciary Committee. The groups, including the Center for Democracy and Technology, Demand Progress, and TechFreedom, called for several surveillance reforms before Section 215 of the USA Patriot Act expires in December.

But the groups largely focused on the CDR program, noting that the NSA has acknowledged that it illegally collected an unknown number of call detail records between 2015 and 2018 due to “technical irregularities.” The groups also noted that the call records program allows the NSA to collect the records of people two degrees of separation away from the original target.

In 2018, the NSA collected 434 million phone records based on authorization to surveil 11 targets, the groups said, citing ODNI disclosures.

“Given the CDR program’s extraordinary breadth, its lack of demonstrated efficacy, and the government’s failure to lawfully implement it, repealing the CDR program is a necessary first step, although not sufficient without other major reforms,” the groups wrote.

Congressional action is needed to end the call records program, said Sharon Bradford Franklin, policy director for the Open Technology Institute at the think tank New America. Since the call records program was voluntarily suspended, there’s no legal impediment to the NSA resuming collection before Section 215 of the Patriot Act expires in December.

Civil liberties groups remain concerned about the scope of the program when it was operating, added Sandra Fulton, government relations director at Free Press Action, a digital liberties group. President Trump’s administration wants to keep the authority for the program even though the NSA suspended it because “the challenges of implementing it outweigh the benefits,” she said.

“It’s unclear that the government can implement the program without massive over-collection,” Fulton added. “We don't support warrantless phone dragnets, and the program has never been proven effective in preventing terrorist attacks.”

Some lawmakers have also called on Congress to end the program. After news reports of unlawful collection of phone records, Sen. Ron Wyden of Oregon suggested that the 2015 USA Freedom Act didn’t restrict the program as much as lawmakers had hoped.

“It is increasingly clear to me that the NSA’s implementation of reforms to the phone records dragnet has been fundamentally flawed,” he said in March. “In my view, the administration must permanently end the phone records program and Congress should refuse to reauthorize it later this year.”