Ten privacy groups have written to the chairman of the Federal Trade Commission asking that Facebook be assessed for its use of super cookies, used by the social networking giant to track users across the internet.

In a letter of complaint (PDF) dated yesterday, the ten groups, Electronic Privacy Information Center, American Civil Liberties Union, American Library Association, Bill of Rights Defense Committee, Center for Digital Democracy, Center for Media and Democracy, Consumer Action, Consumer Watchdog, PrivacyActivism, and Privacy Times all signed the document.

They wrote regarding concerns that Facebook was using persistent cookies and could track users' activity on the web even after they have signed out from the site, describing this as a risk to their privacy and security.

"We would like to bring your attention to new privacy and security risks to American consumers, the secret use of persistent identifiers ("cookies") to track the Internet activity of users even after they have logged off of Facebook, and the company's failure to uphold representations it has made regarding its commitments to protect the privacy of its users," the letter reads, adding that "Facebook's tracking of post-log-out Internet activity violates both the reasonable expectations of consumers and the company's own privacy statements."

The group also believes Facebook's use of "frictionless sharing" and its Timeline and Opengraph features should be audited, with concerns being raised regarding the social networking giant's ability to disclose far larger amounts of users' personal information to its business partners than it has done in the past.

Facebook recently made changes to the controversial tracking cookies after the issue was widely covered by the media, but the confusing way in which users are presented with options to set privacy levels has long been a concern for many.