The planned changes would ensure that content was restricted to factual material relating directly to council services, and include no comment or commentary.
But he said the use of such evidence would be restricted as intelligence agencies would retain control of the material and could veto its use in court.
Personal data about staff can still be restricted, but it is harder for authorities to keep other material secret on the basis that it is confidential or threatens commercial interests than it would be in response to an FOI request.