The campaign to rein in the surveillance of Americans by the National Security Agency has become even more difficult. Congress, in its lame duck session, has used a set of provisions that expand rather than curtail the agency's data-gathering power.

By way of two pieces of legislation, Congress maintained and expanded the NSA's surveillance powers, stunning lawmakers and advocates who tried to rein in the agency following the revelations of NSA contractor whistleblower Edward Snowden.

In a bill now headed for President Barack Obama's desk, Congress gave the agency what civil liberties advocates argue is an unprecedented authority to collect and store data belonging to American citizens.

Additionally, the omnibus spending bill passed by the House on Thursday – intended to keep the government running through most of next year – was stripped of the amendment banning the NSA from conducting "backdoor" surveillance on Americans and insisting that tech companies redesign their products to make them more surveillance-friendly. That amendment had previously passed the House easily in June.

The Intelligence Authorization Act 2015, which will fund intelligence agencies for the next year, passed in a 325-100 vote, with 50 Democrats and 45 Republicans opposing. Through Section 309 of the act, Congress gave unparalleled legal authority to the government's warrantless surveillance powers to allow for "the acquisition, retention, and dissemination" of U.S. phone and Internet data.

Previously, the White House derived this authority only through Executive Order 12333, signed by President Ronald Reagan in the 1980s. However, backers of the provision passed by Congress argue it would actually limit to five years the amount of time communications data could be kept at intelligence agencies, certain exceptions permitting. Reagan's executive didn't impose any kind of time restriction.

"The provisions in the intel authorization appear to be an attempt by Congress to place statutory restrictions on the retention of information collected under Executive Order 12333, which is not subject to court oversight, has not been authorized by Congress, and raises serious privacy concerns," Neema Guliani, legislative counsel with the American Civil Liberties Union, told the National Journal.

"However, these restrictions are far from adequate, contain enormous loopholes, and notably completely exclude the information of non-U.S. persons."

Meanwhile, lawmakers stripped a key amendment from the Defense Appropriations Act under the omnibus spending bill. It would have blocked the NSA and the CIA from insisting on spy-friendly product redesigns on tech companies and would have required a warrant for access to American Internet records collected under Section 702 of the Foreign Intelligence Surveillance Act.

Despite being passed by a vote of 293-123 in June, the Lofgren-Massie amendment wasn't included in the spending bill because the vote for it will be considered under a closed rule. That means members of Congress won't be able to propose amendments on the floor.

The collapse of the Massie-Lofgren amendment would cap a bad year for legislative NSA reform.