All records and accounts of every office, department or agency of the City shall be open to inspection by any citizen, any representative of a civic organization or any representative of the press at all reasonable times and under reasonable regulations established by Council, except records and documents the disclosure of which would tend to defeat the lawful purpose which they are intended to accomplish; provided, however, that in carrying out the provision of this section, the tax return, or any part thereof, of any individual, firm or corporation shall not be made public nor shall statistics or information concerning the personal affairs of any individual or the business of any single firm or corporation be disclosed.