The government will be able to monitor the calls, emails, texts and website visits of everyone in the UK under new legislation set to be announced soon.
The Home Office says the move is key to tackling crime and terrorism, but civil liberties groups have criticised it.
Attempts by the last Labour government to take similar steps failed after huge opposition, including from the Tories.
A new law - which may be announced in the forthcoming Queen's Speech in May - would not allow GCHQ to access the content of emails, calls or messages without a warrant.
But it would enable intelligence officers to identify who an individual or group is in contact with, how often and for how long.
