The official European Union data protection group has criticised Facebook for changing its privacy settings in December to the detriment of its users.
The Article 29 Data Protection Working Party has written a letter (PDF) to the social networking site, describing the change in default privacy settings as "unacceptable".
Modifications to Facebook made at the end of last year meant that more details contained in user profiles were publically displayed by default, including picture, current city, list of friends and fan pages.
Users had previously been given the option of exposing a limited profile or remaining hidden altogether.
Facebook co-founder and chief executive Mark Zuckerberg claimed at the time that the lowering of user privacy was in line with current " social norms".
However, the Working Party has emphasised the need for a Facebook default setting that allows users to limit their profile and connections information to self-selected contacts. Any further access, such as through search engines, should be an explicit choice by the user, said the group.
The Working Party also said that users should be granted maximum control over the profile data that can be accessed by third-party applications on a case-by-case basis, a point that addresses proposed changes put forward by Facebook in March.
The changes will allow the web site to share the personal information of its users with "pre-approved" third-party sites.
Facebook has confirmed that it is reviewing the letter from the Working Party in detail. While the company agrees with some points, it disagrees with others such as the suggested use of pseudonyms on social networks.
"Facebook has always been based on a real name culture, and we fundamentally believe this leads to greater accountability and a safer and more trusted environment for our users," the firm said.
"We feel that Facebook has been in the forefront of all kinds of sites, not just social networking sites, in giving our users granular controls which enable each user to customise many individual settings in order to share, or protect, as much information as they feel comfortable with."
However, according to reports citing inside sources, Facebook will meet later today to discuss the firm's privacy strategy.
The latest row follows a horde of other complaints about the social networking site. Ten privacy groups, including the Electronic Frontier Foundation, the American Civil Liberties Unions and EPIC, filed a complaint with the US Federal Trade Commission in January.
German consumer protection minister Ilse Aigner, meanwhile, wrote an open letter to Facebook in April, expressing her concern for the social network's users after the changes proposed in March.
