Maurice Frankel (London, CFoI): I'm sure the message from the 7 MPs reported by OurKingdom below is sent in good faith, but I believe they are mistaken. The extract from the House of Commons guidance they quote could lead people to draw the wrong conclusion because it is incomplete. It should have said that a public authority may be required to release an MP's correspondence with it unless exemptions apply. Indeed the Parliamentary briefing itself (opens PDF document) goes on to state that "a Member's correspondence may contain data which is personal to the MP and also data which is personal to the constituent" (paragraph 7), and adds that "if a request asks for the personal data of someone [other than the applicant themself] ... then that information will be exempt if its disclosure would contravene any of the data protection principles in the Data Protection Act" (paragraph 19).
The new exemptions proposed by the Maclean bill are therefore not necessary to protect the relationship between MPs and constituents. Disclosure of any letter between an MP and a public authority concerning a constituent's private problem would breach the data protection principles. The actual effect of the Maclean Bill is to extend protection of the the privacy of MPs' correspondence to issues such as policy matters and legislation which should rightfully be open to the public.