Joe Barton and Edward Markey, co-chairman of the Congressional Bi-Partisan Privacy Caucus were prompted into action by a Wall Street Journal article on the use of ETag technology, which companies including Kissmetrics and Microsoft have recently been found using – although both have since stopped doing so.

ETags and Flash local shared objects, another form of super cookie, have been shown by researchers to be used by web companies to re-spawn previously deleted regular cookies, which would allow them to continue tracking user behaviour without their knowledge.

In a letter to FTC chairman Jon Leibowitz, Barton and Markey worry that “this new business practice raises serious privacy concerns and is unacceptable”.

“We believe the usage of super cookies 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,” they write.

An investigation of super-cookie use would fall within the FTC’s mandate to protect Americans from “unfair and deceptive acts or practices”, the congressmen say.

• In other cookie-related news, Facebook is under fire after a researcher discovered that the social network can still gather tracking data from users who encounter ‘Like’ buttons around the web even when they are logged out of their account. The Wall Street Journal has the full story.