Software giant Microsoft has been urged by campaigners to disclose details of the confidentiality of data shared over the Internet communications service Skype.
The signatories of a letter, which including the campaign group Reporters Without Borders, asked the firm to reveal what information is stored and to what extent governments try to access it.
The letter stressed the importance of Skype as a communication tool, saying that the 600 million people worldwide rely on it for voice, video and chat messaging, the Telegraph reports.
It said that many of these people rely on Skype for secure communication, "whether they are activists operating in countries governed by authoritarian regimes, journalists communicating with sensitive sources, or users who wish to talk privately in confidence with business associates, family, or friends."
These users, and those who advise them, the letter says, "face of persistently unclear and confusing statements about the confidentiality of Skype conversations, and in particular the access that governments and other third parties have to Skype user data and communications, the letter added.
According to the paper, Microsoft, which took control of Skype in May 2011, released a statement, saying 'it is reviewing the letter'.