US National Security Agency 'is surveillance leviathan'
Papers that said a US spying programme "touches" 1.6% of internet traffic in fact reveal the vast scale of snooping, a senior security researcher has said.
Officials played down the scale of the operation, comparing US data collection to a small coin on a basketball court.
But Caspar Bowden told the BBC that the National Security Agency (NSA) was a "surveillance leviathan" with no protection for non-US residents.
On Friday, President Barack Obama vowed to be more transparent about US spying.
In the NSA memorandum, the government said that the internet processes 1,826 petabytes of data a day. The NSA comes into contact with about 1.6% of it, but only selects 0.025% of that data for review.
Figures 'utterly meaningless'
The overall effect is that 0.00004% of the world's online activity is reviewed by NSA intelligence analysts, the memorandum said.
The paper added: "If a standard basketball court represented the global communications environment, NSA's total collection would be represented by an area smaller than a dime on that basketball court."
But Mr Bowden said the figures were "utterly meaningless" since the memorandum is vague about where the data is taken from.
He adds: "After subtracting video media and spam, which accounts for most data by volume, 1.6% is an admission the NSA has become a surveillance leviathan."
Mr Bowden also said there was "no privacy restraint or restriction" in the way that the NSA can access the communications of foreigners.
"The reassurances of the NSA document are addressed entirely to the American people. It simply disregards the human right to privacy of the rest of the world," Mr Bowden said.
Mr Bowden had warned the European Parliament about the reach of US surveillance before a series of leaks by former US intelligence contractor Edward Snowden exposed the existence of widespread electronic surveillance.
On Friday the Obama administration also released a policy document outlining its legal rationale for collecting telephone metadata.
It said that to be able to spot a suspicious pattern of behaviour it must have access to a sufficiently large set of data.
The US government needed to keep those records itself for up to five years because telephone companies normally do not keep their own records that long.
The papers appeared hours after Mr Obama told reporters he would take action to be more transparent about US surveillance plans.
He proposed making changes to the Patriot Act, under which the NSA programme is authorised, and reforming the secret court that approves surveillance requests.
The president added that he would appoint a privacy and civil liberties officer to the NSA and also create a task force that would make further recommendations on improving transparency.