President Obama said today that the "modest encroachments on privacy" involved in intelligence agencies monitoring phone calls and Internet activity were worth it because they help "prevent terrorist attacks".
He added that the monitoring of Internet activity "does not apply to US citizens and it does not apply to people living in United States".
The Foreign Secretary said British intelligence would never use its partnership with the United States to get around UK laws.
GCHQ (Government Communications Headquarters) is one of three UK intelligence agencies that form the UK's security and intelligence system.
Facebook, Google and Microsoft have all denied claims that they cooperated with US intelligence agencies to gather data on foreign users.