Children's advocacy groups fired at Facebook, rejecting a $US20 million ($A22.38 million) deal made to settle charges that the social network violated privacy by using "likes" as endorsements for ads.
US-based Public Citizen led organisations backing a legal brief urging a federal appeals court in San Francisco to toss the deal inked last year.
The filing said the settlement fails to compel the social network to change its ways when it comes to using profile images of teenage members in ads without the consent of parents or guardians.
The practice is specifically banned by laws in California and six other US states, according to Public Citizen lawyer Scott Michelman.
"The capture and republication of teen postings by Facebook is a pernicious assault on their rights to decide where their messages should go," said Robert Fellmeth, director of the Children's Advocacy Institute at the University of San Diego School of Law, which is representing another challenger to the settlement.
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A US judge in August approved the deal in August to make Facebook pay for using members "likes" as endorsements for ads.
The pot of money is to be divvied up among lawyers, internet privacy rights groups and Facebook users who filed claims in the class-action lawsuit.
Those turning on the deal include Campaign for a Commercial-Free Childhood, which is in line to receive $US290,000 ($A324,530) of that Facebook money if the settlement deal survives appeals lodged against it.
Under the terms of the deal, California-based Facebook would to let parents control how their children's likes and posts are used, or not use them by default if children's parents are not on the social network.
Public Citizen has joined those calling for posts or likes by those younger than 18 years old to be automatically made off-limits for ads.
The judge who signed off on the settlement reasoned that the deal was fair given the challenges of proving Facebook members were financially harmed or that signaling "likes" for products didn't imply consent.
