The department will ask States members to approve the extension next month.
An extra three years was necessary, it said, because the current brief is due to expire in November and it wanted it to remain in place until the new Island Development Plan was implemented in 2016.
The planning brief for the Leale's Yard Mixed Use Redevelopment Area provides guidance to prospective developers.
Permission in principle was granted for the redevelopment of the main Leale's Yard site to provide retail and residential units in February 2011.
