Declan McCullagh/CNET

The National Security Agency has quietly discontinued a controversial program put in place after the September 11 terrorist attacks that collected and analyzed millions of Americans' domestic calls and texts, according to a senior Republican congressional aide.

The NSA hasn't used the system in months, and the Trump administration might not seek to renew its legal authority, Luke Murray, the national security advisor for House minority leader Kevin McCarty (R-Calif.), said in a podcast Saturday.

Under a controversial national security policy put in place by the Patriot Act in 2001, the NSA had been collecting large amounts of metadata, the digital information that accompanies electronic communications. That information included what phone numbers were on the call, when the call was placed and how long it lasted, which was then saved in a database.

Former NSA contractor Edward Snowden intensified already heated debate over the Patriot Act programs in 2013 when he leaked documents detailing the ways in which the secretive US government agency was collecting data. A new system put in place by Congress in 2015 required federal agencies to seek a court order on a case-by-case basis to obtain call data from telephone companies.

The USA Freedom Act of 2015, legislation designed to curtail the federal government's sweeping surveillance of millions of Americans' phone records, is set to expire at the end of year, if the Trump administration doesn't ask Congress to renew its authority to continue the program.

Murray raised doubts about whether congressional debate about renewing the program would be necessary during a discussion on national security issues with Lawfareblog.com.

"The administration actually hasn't been using it for the past six months because of problems with the way in which that information was collected," Murray said. "I'm not actually certain that the administration will want to start that back up given where they've been in the past six months."

The NSA declined to comment. The White House didn't immediately respond to a request for comment.