In an open letter published on November 3 by the German news magazine Der Spiegel, whistleblower Edward Snowden accused the U.S. National Security Agency (NSA) and its British counterpart (GCHQ) of being among the “worst offenders” engaged in uncontrolled mass surveillance.

In his letter, entitled “A Manifesto for the Truth,” Snowden wrote: “The world has learned a lot in a short amount of time about irresponsibly operated security agencies and, at times, criminal surveillance programs. Sometimes the agencies try to avoid controls.”