asked the Secretary of State for the Home Department if he will list those topics on which it is not his practice to answer parliamentary Questions; and if he will list any changes in practice since 1972, indicating in each case the date on which the change was made and the relevant reference in the Official Report.

It would not be possible to give a definitive and exhaustive list of the topics on which I might judge it right not to give information in reply to a particular Question; the prevention and detection of crime, the security of the State, and privacy and commercial confidence are among the relevant considerations. There have been no changes in practice since March 1974.