BERLIN, May 4 (Xinhua) -- German justice minister Katarina Barley (SPD) has demanded further improvements to Facebook's management of private user data, German media reported on Friday.

Several publications participating in the "Redaktionsnetzwerk Deutschland" (RND) editorial network cited a new letter sent by Barley to Facebook founder and chief executive officer (CEO) Mark Zuckerberg.

In the document, the justice minister welcomed announcements from the U.S. social media company to change its available privacy settings for users. However, Barley also warned that additional steps would still have to be taken in response to revelations surrounding the misuse of data by the London-based election strategy campaign company Cambridge Analytica.

Barley demanded more transparency and better control for users over the use of their data, adding that corresponding changes would have to be "implemented rapidly".

Additionally, Barley called for the creation of new internal supervisory mechanisms to ensure that formal guidelines were actually being upheld in Facebook's dealings with third party advertising clients.

Barley wrote that Facebook had so far failed to assume responsibility for its inappropriate corporate behaviour and criticized plans to transfer the storage of user data from the European Union (EU) to the U.S.

European users of the service currently benefited from enhanced online privacy protection enshrined in EU law.

The minister argued that the commercial sale of user data by Facebook directly affected key rights enjoyed by citizens. She described the use of such sensitive data to politically influence or manipulate voters as "inacceptable" in states where the rule of law applied.

Facebook has admitted that the data of up to 87 million users was passed on illegally to Cambridge Analytica. The information was used in an attempt to support the election campaign of U.S. president Donald Trump. Up to 310,000 Germans were affected by the scandal as well.