Intelligence Services Act 1994

3 The Government Communications Headquarters

(1) There shall continue to be a Government Communications Headquarters under the authority of the Secretary of State; and, subject to subsection (2) below, its functions shall be—

(a) to monitor or interfere with electromagnetic, acoustic and other emissions and any equipment producing such emissions and to obtain and provide information derived from or related to such emissions or equipment and from encrypted material; and

(b) to provide advice and assistance about—

(i) languages, including terminology used for technical matters, and

(ii) cryptography and other matters relating to the protection of information and other material,

to the armed forces of the Crown, to Her Majesty’s Government in the United Kingdom or to a Northern Ireland Department or to any other organisation which is determined for the purposes of this section in such manner as may be specified by the Prime Minister.

(2) The functions referred to in subsection (1)(a) above shall be exercisable only—

(a) in the interests of national security, with particular reference to the defence and foreign policies of Her Majesty’s Government in the United Kingdom; or

(b) in the interests of the economic well-being of the United Kingdom in relation to the actions or intentions of persons outside the British Islands; or

(c) in support of the prevention or detection of serious crime.

(3) In this Act the expression “GCHQ” refers to the Government Communications Headquarters and to any unit or part of a unit of the armed forces of the Crown which is for the time being required by the Secretary of State to assist the Government Communications Headquarters in carrying out its functions.