The Observer reports: Senior figures inside British intelligence have been alarmed by GCHQ’s secret decision to tap into transatlantic cables in order to engage in the bulk interception of phone calls and internet traffic.

According to one source who has been directly involved in GCHQ operations, concerns were expressed when the project was being discussed internally in 2008: “We felt we were starting to overstep the mark with some of it. People from MI5 were complaining that they were going too far from a civil liberties perspective … We all had reservations about it, because we all thought: ‘If this was used against us, we wouldn’t stand a chance’.”

The Guardian revealed on Friday that GCHQ has placed more than 200 probes on transatlantic cables and is processing 600m “telephone events” a day as well as up to 39m gigabytes of internet traffic. Using a programme codenamed Tempora, it can store and analyse voice recordings, the content of emails, entries on Facebook, the use of websites as well as the “metadata” which records who has contacted who. The programme is shared with GCHQ’s American partner, the National Security Agency.