In 1966, in what has become known as the Wilson Doctrine, the Prime Minister, Harold Wilson, informed Parliament that he had issued an instruction that the telephones of parliamentarians were not to be intercepted by the intelligence and security agencies. Subsequent Prime Ministers have all expressed their continued commitment to the Wilson Doctrine. This article examines the nature and limitations of the Wilson Doctrine, and its continued application in the context of recent legislative changes and a number of prominent recent cases. It focuses on apparent changes to the scope and attempts to set aside the Wilson Doctrine under the Blair government and the implications of the interception of the communications of Sinn Fein Members of Parliament, and the bugging of meetings involving the Labour MP Sadiq Khan. © 2013 Taylor & Francis.