Merkel was faced with a public backlash against mass surveillance when it was revealed by former CIA operative Edward Snowden that the British intelligence monitoring agency GCHQ and US National Security Agency (NSA) had been running two mass surveillance programs — Prism and Tempora — used to collect vast amounts of communications data.
Obama promised her the US was "not monitoring and will not monitor" her communications but German diplomatic sources said they were still not satisfied with the White House's explanation.
It emerged later, however, from sources including former NSA contractor Edward Snowden, that the US embassy in Berlin, overlooking the Reichstag, was being used as a base for a special unit of the CIA and NSA to monitor a large part of cell phone communications in the government district. This further twist saw Merkel come under pressure to investigate all the activities of the NSA, GCHQ and Germany's own intelligence service, BND.
Germany is not a member of the Five Eyes alliance — the US, UK, Australia, Canada and News Zealand — that share intelligence information on a regular basis. Although Britain does share intelligence with the German intel agency, it is highly unusual for a British prime minister and the chiefs of the three intelligence services to brief a German Chancellor in person.