US law enforcement and intelligence agencies are collecting massive amounts of data on Americans and storing it for too long, creating a potential for abuse, a research report said Tuesday.

The report by Brennan Center for Justice at New York University found that data collection and storage on Americans, often with no connection to terrorist threats, create "opportunities for abuse and clogging government databases."

The report found fault with policies of the FBI and National Security Agency, which have stepped up data collection and sharing since the attacks of September 11, 2001.

"Intelligence agencies are treating the chaff much the same as the wheat," said Rachel Levinson-Waldman, author of the report.

"We expect the government to collect and share information that is critical to national security, but creating an electronic dossier on every American citizen is inefficient and ineffective. We need modern policies that limit how and with whom innocent Americans' data can be shared and stored."

The Brennan report said that in addition to the NSA -- which has come under fire following revelations of huge data collection efforts -- other agencies including the Department of Homeland Security and FBI also keep too much data too long.

"The collection and retention of non-criminal information about Americans for law enforcement and national security purposes poses profound challenges to our democracy and our liberties," the report said.

The researchers expressed concern about so-called "suspicious activity reports" used by federal, state, and local authorities to provide information to the federal government, as well as FBI investigations and "national security letters," which are secret subpoenas used by federal agents.

They also said there were few controls on electronic searches at border crossings of computers, camera and other electronic devices.

"Depending on the data set, presumptively innocuous information may be retained for periods ranging from two weeks to five years to 75 years or more," the report said.

The report, described as the first comprehensive look at how Americans' data is collected, stored and shared, the Brennan Center cited numerous opportunities for misuse,

"The FBI's policy is to keep all information it gathers -- regardless of whether it's on innocent Americans or is relevant to an investigation -- for 20 to 30 years," the report said.

It added that in the five years after the 2001 attacks, the FBI "improperly gathered and retained information on individuals because of their political and social activism," according to a Justice Department audit.

The NSA, according to the report's citing of a 2012 audit, "broke privacy rules thousands of times between 2011 and 2012," by acquiring information on more than 3,000 Americans and green-card holders with no connection to terrorism.

The report said Americans' electronic communications may be accessed without a warrant and kept for up to six years under NSA guidelines.

Recommendations in the report include prohibiting retention and sharing of domestically gathered data "without reasonable suspicion of criminal activity."

The researchers also called for boosting oversight over the National Counterterrorism Center, requiring regular audits and updating the Privacy Act of 1974.

The report comes amid a firestorm over NSA surveillance programs revealed by former intelligence contractor Edward Snowden, which show collection of phone records and emails on a wide scale.