Auckland Mayor Len Brown is sitting on secret documents about controversial plans which would make up to three-storey apartments possible in half of residential Auckland.

The Herald asked Mr Brown on Tuesday to release documents used to draw up the mixed housing and terraced housing and apartment zones in the new planning rulebook, or Unitary Plan.

The request was made under the emergency provisions of the Local Government Official Information and Meetings Act so they could be made public before feedback on the draft plan closes on May 31. Last night, a spokesman for Mr Brown said the mayor's office was working through the request and would provide a response shortly.

The documents were the basis for a political working party to develop heights and controls for the two zones that have a profound effect on more than half of residential Auckland. The working party, which meets behind closed doors, makes recommendations to the Auckland Plan committee which discusses issues in public.

A member of the political working party said officers provided no in-depth analysis on the two zones and had belatedly revealed the three-storey height limit in the mixed housing zone.