Interception of Communications Act 1985
Report presented to parliament that deals with the Secretary of States power to issue interception warrants at the request of the intelligence and security agencies.
http://www.official-documents.co.uk/document/cm47/4778/4778.htm

Regulation of Investigatory Powers Act 2000
Provides for the interception of user logs and e-mails of suspected criminals by the security and intelligence services.
http://www.hmso.gov.uk/acts/acts2000/20000023.htm

Terrorism Act 2000
Act detailing the legal measures that are available in the prevention of terrorism.
http://www.hmso.gov.uk/acts/acts2000/20000011.htm