FBI spies on how many?

The US House Judiciary Committee has sent a letter to the director of national intelligence James Clapper asking him exactly how many US citizens the security services are spying on.

"We write to ask that you provide us with a public estimate of the number of communications or transactions involving United States persons subject to Section 702 surveillance," the letter reads.

It notes that some members the committee have been asking for the information for five years, and highlights a number of other groups that have done the same. And it strongly implies that if Clapper doesn't come up with a figure this year, the committee will not renew the relevant part of the Foreign Intelligence Surveillance Act in 2017.

In an effort to pre-empt Clapper's most obvious responses, the letter specifically notes it does not want an exact number but "a rough estimate." And it notes that even civil liberties groups are happy for the data to be sampled once in order to give an effective estimate.

The committee gives Clapper until May 6 to come up with a plan. ®