Sir Tim Berners-Lee, the inventor of the World Wide Web, said the revelations were "deeply concerning".
He said: "I call on all web users to demand better legal protection and due process safeguards for the privacy of their online communications, including their right to be informed when someone requests or stores their data."
Nick Pickles, director of campaign group Big Brother Watch, said: "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."
