In an interview with Russia Today Assange said Facebook was one of the top tools for the U.S. Government to spy on its citizens.

'Here we have the world's most comprehensive database about people, their relationships, their names, their addresses, their locations, their communications with each other and their relatives, all sitting within the United States, all accessible to U.S. Intelligence,' he said.

'Facebook, Google, Yahoo, all these major U.S. organisations have built-in interfaces for U.S. intelligence.

'Everyone should understand that when they add their friends to Facebook they are doing free work for the United States intelligence agencies,' he added.

A spokesman for Facebook denied the company was doing anything they weren't legally obliged to do, in an email to the New York Daily News.

'We don't respond to pressure, we respond to compulsory legal process,' the spokesperson wrote.

'There has never been a time we have been pressured to turn over data - we fight every time we believe the legal process is insufficient.'

That said there are concerns about the way Facebook shares its information and with who.

Last year three Democratic senators requested that the FTC look at Facebook's information-sharing policies.

Apps like Farmville and Causes also shared users' information with advertising and tracking companies, according to the Wall Street Journal