WASHINGTON  Signaling a sea change in the debate over Internet privacy, the government’s top consumer protection agency on Wednesday advocated a plan that would let consumers choose whether they want their Internet browsing and buying habits monitored.

Saying that online companies have failed to protect the privacy of Internet users, the Federal Trade Commission recommended a broad framework for commercial use of Web consumer data, including a simple and universal “do not track” mechanism that would essentially give consumers the type of control they gained over marketers with the national “do not call” registry.

Those measures, if widely used, could directly affect the billions of dollars in business done by online advertising companies and by technology giants like Google that collect highly focused information about consumers that can be used to deliver personalized advertising to them.

While the report is critical of many current industry practices, the commission will probably need the help of Congress to enact some of its recommendations. For now, the trade commission hopes to adopt an approach that it calls “privacy by design,” where companies are required to build protections into their everyday business practices.