If two or more lots or a combination of lots and portions of lots with continuous frontage in a single ownership are of record at the time of passage or amendment of this Part and if all or part of the lots with no buildings do not meet the requirements established for lot width and area, the lands involved shall be considered to be an undivided parcel for the purposes of this Zoning Code and no portion of the parcel shall be used or sold in a manner which diminishes compliance with lot width and area requirements established by this Zoning Code, nor shall any division of any parcel be made which creates a lot with a width or area below the requirements stated in this Zoning Code.