The East building is the largest new structure being developed at the $1 billion Britomart precinct in Auckland.

Hawkins Construction, owned by McConnell family interests, is putting up the block where work had this week reached level six.

The East building will be 13 levels when it is finished.

The block is rising at the intersection of Britomart Place and Galway St, behind the old Wharf Police Station which held its official opening last night.

That former station, refurbished and restored by Phillimore Properties, has been leased to bar Brew On Quay.

The East building is 85 per cent pre-leased to Westpac and Ernst & Young but developer Cooper & Company is searching for more tenants.

Construction is not expected to finish for another two years. Bank staff have moved into the Charter Customs Building which was opened in March.

Chris Hunter, Hawkin's chief executive, said the East building was on a prominent site and part of the larger development which would be finished in early 2011.

"Our project is at the Britomart Place end of the central precinct. This is a major development which consists of two medium-rise towers - the Ernst & Young Building to the north and the Westpac Building to the south - both named for their confirmed anchor tenants.

"The two towers will be bridged at the top by three floors of boutique private office space to be known as Britomart Place and accessed by an exclusive entrance on the eastern side. Works are being undertaken to ensure the historical characteristics of the building are upheld while introducing modern new sustainable buildings to the precinct.

"The main commercial lobby of the Ernst & Young Building will front Takutai Square, the central public space within the precinct. This lobby will be partially occupied by a cafe that opens out onto the square to the western edge," Hunter said.

Te Ara Tahuhu, a pedestrian thoroughfare, will run between the two towers at ground level from Takutai Square to Britomart Place and allow access to the Britomart train station.

The new developments are designed to achieve a New Zealand Green Building Council five-star rating and Hunter said the project was one of the most environmentally friendly Hawkins had been involved in.

Challenges included constructing East in a "live working environment", Hunter said. "Not only are we building in Auckland's busy CBD where vehicle movements and pedestrian traffic dominates but we are also are building on top of the railway corridor and Britomart station which sits under this precinct," he said.