Curtailing the scope of the NSA's controversial data mining won't impede national intelligence gathering, a presidential panel told lawmakers today.

The President's Review Group on Intelligence and Communications Technologies appeared before the Senate Judiciary Committee to discuss its 46 recommendations that limits the National Security Agency's vacuuming of data.

President Obama is set to announce on Friday changes addressing the privacy concerns about the NSA's operations that have been brought to light by former agency contractor Edward Snowden.

"Not one of the 46 recommendations in our report would, in our view, compromise and jeopardize that ability [to gather intelligence] in any way," said Harvard Law School Professor Cass Sunstein, speaking for the Review Group's five members.

The panel sought unanimity in arriving at its recommendations and ultimately voted 230 times as changes were made to the recommendations, he said.

The most attention-getting item calls for phone companies to hold onto the millions of metadata records currently stored by the NSA. Metadata includes phone numbers, origination points and duration of phone calls or email messages but not their content.

The Review Group members explained that they are concerned about the possibility of future privacy abuses by the government if that data remained with a government agency.

Geoffrey Stone, a constitutional law expert at the University of Chicago, told lawmakers that the "primary danger" is not how the data is currently used, but rather how it leaves "sitting out there a huge amount of information - personal information about Americans - that could be abused in awful ways."

If the government continues to hold onto metadata, it leaves opens the possibility of future abuse by someone seeking "political dirt" on an individual and their activities "and that that's a danger that we want to avoid," Stone said.

The panel said that while the NSA's metadata gathering program has not had a huge impact on existing terrorism cases, it only has to be successful once to prove its worth.

"One of the ways that I think about this is, many of us have never suffered a fire in our homes, but we still all have homeowners' insurance to protect against that, " said former CIA Acting Director Mike Morell.

The NSA has repeatedly noted that the metadata it gathers does not include the content of phone calls or e-mails. But Morell said that because of his work on the panel he had come to realize "that there is quite a bit of content in metadata."

"When you have the records of the phone calls that a particular individual made, you can learn an awful lot about that person," Morell said. "And that's one of the things that struck me. So there's not, in my mind, a sharp distinction between metadata and content. It's more of a continuum."

Phone companies have expressed concerns about becoming the repositories of metadata, Stone said, and acknowledged that they might be susceptible to hacking in the private sector. But the Review Group saw that possibility as a lesser evil than the potential for government abuse of the data, he said.

The panel as a whole did not want to respond to questions about whether the existing NSA program could have prevented the 9/11 attacks if it had been in existence at the time.

Dick Clarke, who ran the counter-terrorism office in the Bush White House, said "it's impossible to go back and reconstruct history."

The real issue prior to 9/11 was how the various intelligence and law-enforcement agencies did not share information as well as they should have, Clarke said.

However, Morell wrote a Washington Post piece where he stated his belief that the NSA program could have had an impact. At today's hearing, Morell explained several times that what he was stating in the op-ed piece was his personal opinion and not that of the Review Group.