Lawmakers are keeping the Federal Trade Commission busy, requesting that the agency investigate potential privacy issues.

Reps. Ed Markey (D-Mass.) and Joe Barton (R-Tex.) sent a letter asking that the agency investigate the use of “supercookies” by Web sites, which they contend constitutes an unfair and deceptive practice. “Supercookies” are different from regular cookies, which consumers can delete if they do not want to be tracked online. Instead, new technologies allow companies to track consumers online by hiding files in Web browsers that cannot be deleted and can be re-created even after the deletion of regular cookies.

“As Co-Chairs of the Congressional Bi-Partisan Privacy Caucus, we believe this new business practice raises serious privacy concerns and is unacceptable. We are also very concerned about the extent of this practice by websites as well as the impact supercookies have on consumers. Furthermore, we believe the usage of supercookies takes away consumer control over their own personal information, presents a greater opportunity for the misuse of personal information, and provides another way for consumers to be tracked online,” the legislators wrote.

The letter noted that sites such as MSN.com and Hulu.com have used supercookies to track consumers, according to a report in The Wall Street Journal.

In a separate letter to the agency, Sen. Charles Schumer (D-N.Y.) asked the FTC to investigate a new policy announced by OnStar, the GPS tracking company.

In September, OnStar said it planned to continue to track drivers and sell their data to third parties even after they cancelled the service. The company said maintaining a connection would make it easier for consumers to reenroll and would enable the company to provide customers with information about recalls affecting their vehicles and natural disasters. Although OnStar said consumers could specifically request not to be tracked, the request would need to be explicit and in addition to a request to terminate service.

Calling the policy change a “brazen invasion” of consumer privacy, Sen. Schumer said it “put consumers at risk for having sensitive personal data collected and shared without their knowledge.”

An estimated six million Americans currently have OnStar installed in their vehicles, according to the letter, and most new General Motors vehicles come standard with the device, potentially impacting millions more consumers.

But just days after Sen. Schumer sent his letter requesting an investigation into whether the practice constituted an unfair and deceptive practice, OnStar reversed its position.

In a press release, the company said it no longer planned to keep a data connection to customers’ vehicles after OnStar service is cancelled.

“We realize that our proposed amendments did not satisfy our subscribers,” said OnStar president Linda Marshall in the statement. “This is why we are leaving the decision in our customers’ hands. We listened, we responded and we hope to maintain the trust of our more than 6 million customers.”

If the company ever offers the option of a data connection after cancellation, it said it would only be in situations where consumers affirmatively opt in, and would “honor customers’ preferences about how data from that connection is treated.”

“We regret any confusion or concern we may have caused,” Marshall said.

To read the letter from Reps. Markey and Barton, click here.

To read Sen. Schumer’s letter, click here.

Why it matters: Under current law, both the use of supercookies and OnStar’s policy change are legal. But the negative public reaction, coupled with possible privacy legislation and regulation on the horizon, could add to support for measures such as a Do-Not-Track mechanism.