U.S. lacks plan for digital TV switch: study

"This raises uncertainty, including whether consumers, particularly underserved and otherwise vulnerable populations, will have the information necessary to respond to the transition and to maintain their access to television programming," the GAO report said.

The GAO report rekindled concerns among some Democratic lawmakers in Congress, who fear the agency is relying too heavily on voluntary industry efforts to notify consumers.

"Without a comprehensive plan that also addresses managing risks and mitigating against potential problems, tens of millions of consumers could be adversely affected and this important transition put needlessly in jeopardy," Democratic Rep. Edward Markey, of Massachusetts, said in a statement.

(Reporting by Peter Kaplan; editing by Carol Bishopric)