Facebook privacy campaign group europe-v-facebook plans to sue the social network in Ireland, where the company has its international headquarters, it said on Tuesday.
The Austrian student group has been campaigning for better data protection by Facebook for over a year and has won some concessions, notably pushing the world's biggest social network to switch off its facial recognition feature in Europe.
But the group said on Tuesday the changes did not go far enough and it was disappointed with the response of the Irish Data Protection Commissioner, which had carried out an investigation after europe-v-facebook filed numerous complaints.
"The Irish authority is miles away from other European data protection authorities in its understanding of the law, and failed to investigate many things. Facebook also gave the authority the runaround," it said in a statement.
"We are hoping for a legally compliant solution from the Irish data protection authority. Unfortunately, that is highly doubtful at the moment. Therefore we are also preparing ourselves for a lawsuit in Ireland."
Facebook is also facing a class-action lawsuit in the United States, where it is charged with violating privacy rights by publicising users' "likes" without giving them a way to opt out.
A U.S. judge late on Monday gave his preliminary approval to a second attempt to settle the case by paying users up to $10 each out of a settlement fund of $20 million.