A British parliamentary committee accused Facebook on Wednesday of giving companies such as Netflix preferential access to users' data even after it tightened its privacy rules in 2014-15.
The UK parliament's select media committee published more than 200 pages of internal Facebook emails it has acquired while probing how the giant was being used to manipulate major election results.
The emails feature in a case being heard in a California court filed against the giant by the now-defunct US app developer Six4Three.
Committee chair Damian Collins said it was not clear from the private exchanges between Facebook and app developers whether users were aware that their friends list and other private information was being used.
"Facebook have clearly entered into whitelisting agreements with certain companies, which meant that after the platform changes in 2014/15 they maintained full access to friends data," Collins wrote in an accompanying note.
"The idea of linking access to friends data to the financial value of the developers relationship with Facebook is a recurring feature of the documents."
Facebook said in a statement released to AFP that the Six4Three emails "are only part of the story and are presented in a way that is very misleading without additional context".
The social media behemoth launched a public campaign in 2014 aimed at easing user concerns about data breaches.
But the emails suggest that Facebook followed a set policy of selling the information to a select group of major app developers even after the platform changes were fully deployed in 2015.
The emails show Facebook owner Mark Zuckerberg mulling charging app developers for data access in 2012.
Facebook's director of developer platforms and programs Konstantinos Papamiltiadis told AFP last week that the company "has never sold anyone's data".