According to The Guardian, the UK's security agency GCHQ (Government Communications Headquarters) has been secretly gathering intelligence from the world's biggest Internet companies through a covert operation called PRISM, which is run by the NSA (the US National Security Agency).
The Guardian says it has obtained documents which reveal that "GCHQ, based in Cheltenham, has had access to the system since at least June 2010, and generated 197 intelligence reports from it last year. The US-run programme, called Prism, would appear to allow GCHQ to circumvent the formal legal process required to seek personal material such as emails, photos and videos from an internet company based outside the UK."
So, now it's no longer a "conspiracy theory."
Nick Pickles: “There are legal processes to request information about British citizens using American services and if they are being circumvented by using these NSA spying arrangements then that would be a very serious issue... If British citizens have had their emails and social media messages seized by the US Government without any justification or legal authority, serious questions must be asked at the highest levels. The revelations call into question the integrity of cloud services that are used by millions of non-US citizens every day... Surveillance without suspicion is an affront to a free society and it is essential that we get to the bottom of the NSA and US Government has being doing and how British citizens may have seen their privacy compromised on a vast scale.”
2) "PRISM Collection Details", via the Washington Post (http://www.washingtonpost.com/wp-srv/special/politics/prism-collection-documents/).