"Because these proposed changes raise privacy risks for users, may be contrary to law, and violate your previous commitments to users about site governance, we urge you to withdraw the proposed changes," wrote CDD President Jeffrey Chester and EPIC President Marc Rotenberg.
Facebook unveiled the proposed changes last week, which include ending its user-voting system and implementing new tools for managing Facebook messages. Users have until Nov. 28 to review and comment on the changes before Facebook adopts them.
The two privacy groups contend that Facebook's plans to eliminate its user-voting process "raises questions about [its] willingness to take seriously the participation of Facebook users."
Facebook started letting users vote on proposed changes to its governing documents in 2009. If a blog post about a proposed change received 7,000 user comments within 30 days, the change would be put to a vote.
But the social network found that this voting process "actually resulted in a system that incentivized the quantity of comments over their quality," Elliot Schrage, vice president of communications and public policy at Facebook, wrote in a blog post last week about the proposed changes.
"Therefore, we’re proposing to end the voting component of the process in favor of a system that leads to more meaningful feedback and engagement," Schrage said.
He added that Facebook will continue to post significant changes to its data use policy and Statement of Rights and Responsibilities, as well as give users a seven-day period to review and comment on them.
The two privacy groups argue that the proposed new tools for Facebook's messaging system could increase the amount of spam users receive, leaving them more vulnerable to being targeted by online scammers.
CDD and EPIC also warned that Facebook added a section to its data use policy that could directly affect Instagram users because it lets the social network share information with its affiliates. By adding this new section, Facebook "could combine user profiles and freely share user data between" photo-sharing service Instagram and the social network, the privacy groups warned.
Facebook acquired Instagram earlier this year.
The groups note that Facebook's recent settlement with the FTC requires the social network to "obtain the affirmative express consent of its users" to share their personal information with a third party before it starts sharing any data.
Facebook spokesman Andrew Noyes declined to comment on the letter from CDD and EPIC.
The letter to Zuckerberg was also sent to all five FTC commissioners and lawmakers with leadership roles on committees with jurisdiction over privacy issues.