British intelligence agencies have the capacity to monitor social media sites such as Facebook and YouTube by tapping into the cables carrying the world's internet traffic, according to documents obtained by NBC News.
The documents, reportedly taken from the US National Security Agency by whistleblower Edward Snowden, show British spies demonstrated a pilot programme to their US counterparts in 2012.
The programme, called "Squeaky Dolphin", was able to monitor YouTube in real time, collect addresses and some other user information.
According to the “Psychology A New Kind of SIGDEV [Signals Development] presentation, the Government was also able to take part in “broad real-time monitoring of online activity” of URLs “liked” on Facebook, Blogspot/Blogger visits and Twitter.
US whistleblower Edward Snowden has alleged the National Security Agency went beyond its brief to spy on German companies that were rivalling American firms.
The intelligence leaker, who has been granted a year's asylum by Russia, made the claims in an interview with German television channel ARD.
Mr Snowden said: "If there is information at (German engineering firm) Siemens that (the NSA) think would be beneficial to the national interests, not the national security, of the United States, they will go after that information and they'll take it."
Mr Snowden also said during the interview that he believed US officials wanted to kill him after his series of leaks exposed a wide scope of security practices, including the bugging of international leaders' phones.
The head of the U.S. Senate Intelligence Committee has objected to President Barack Obama's proposal for the government to give up control of the storage of the telephone records of millions of Americans it holds as part of its counter-terrorism efforts.
Signaling congressional opposition to the change, Democratic Senator Dianne Feinstein, who heads the intelligence panel, criticized the idea of moving the data out of government control.
"I think a lot of the privacy people (advocates) perhaps don't understand that we still occupy the role of the 'Great Satan,' new bombs are being devised, new terrorists are emerging, new groups - actually, a new level of viciousness. And I think we need to be prepared," she told the NBC.
Obama on Friday announced an overhaul of U.S. surveillance activities following criticism sparked by the disclosure of leaked documents exposing the wide reach of National Security Agency spy efforts.
The European Commission has said Barack Obama's reforms to the National Security Agency are important steps towards rebuilding trust between the US and the EU.
President Obama has ordered curbs on practices by US intelligence agencies, promising to end the surveillance of world leaders and officials.
"Trust in EU-US data flows has been affected by revelations on these intelligence programmes and needs to be rebuilt. In recognising the need for action, President Obama has taken important steps towards rebuilding that trust," a statement from the European Commission read.
The existence of the US intelligence programme that allegedly monitored the phone of Germany's chancellor Angela Merkel concerned EU leaders.
A legal adviser to Edward Snowden said that Barack Obama's swipe at the US intelligence leaker in his speech on Friday was "unnecessary" and framed the privacy issue in a false way of making people choose between liberty and security.
Jesselyn Radack, the national security and human rights director at the Government Accountability Project, said: "His unnecessary swipe at Snowden for the unauthorized disclosure ... was really unwarranted."
President Obama unveiled NSA reforms during a long-awaited speech that balanced pledges to increase privacy protections with a warning that intelligence gathering would continue.
President Obama's "acknowledgement of the need for a full and public debate" has been welcomed by shadow foreign secretary Douglas Alexander.
Mr Alexander said that is no longer enough for oversight to be used as a reason by security services.
The debate on spying has only just begun, said Guardian journalist Glenn Greenwald who published the revelations of NSA whistleblower Edward Snowden.
Responding to reforms on surveillance announced by President Obama today, Mr Greenwald told Channel 4 News: "There are some changes, some which are substantive such as putting an actual advocate in the Fisa court so not only the government is heard from.
"I think the problem is the fundamental nature of the NSA that has created worldwide controversy namely spying on people by the hundreds of millions without suspicion, will continue to endure".
President Obama's speech on security and privacy reforms were "embarrassing", Wikileaks founder Julian Assange has said.
Mr Assange, who has been inside the Ecuadorian Embassy in London for more than a year to avoid extradition to the US told CNN: "I think it's embarrassing for a head of state to go on for 45 minutes and say almost nothing.
"It's clear that the president would not be speaking here today if it were not for the actions of Edward Snowden and whistleblowers before him...these whistleblowers have forced this debate. This president has been dragged kicking and screaming to today's address", he added.
"Unfortunately today we also see very few concrete reforms".
This was the long awaited speech by the President on the limits of data collection and intelligence gathering. Of course, prompted by the spectacular leaks by the NSA contractor Edward Snowden.
The President made no apology for US spying, but he acknowledges that there has been a breach of privacy and in trust. So he made promises to America's friends and allies around the world.
I think it is fair to say that somewhere in Russia or wherever he is hiding, Snowden himself will see this as something of a personal victory for it is crystal clear that this speech and this national debate that is going on across America would not be happening without Snowden's intervention.
The British Government has been urged to follow Barack Obama's example in increasing the oversight and accountability of intelligence agencies.
Nick Pickles, the director of privacy campaigners Big Brother Watch, said that Britain was "lagging behind" the US in terms of surveillance.