What is interception?
Interception means the interception of communication in the course of its transmission via a postal service or telecommunications system (such as a telephone or computer) so as to make it available to a third party.
The law permits interception of communications by law enforcement and intelligence agencies in tightly controlled circumstances.
Interception can only be authorised:
in the interests of national security
preventing or detecting serious crime
safeguarding the economic well-being of the UK.
Roughly 2,000 intercept warrants are authorised a year (Source: the Interception of Communications Commissioner's report for 2007). Read the Interception code of practice