King's House will be put on the market in a matter of months.
The city council’s seafront offices will be put up for sale at the start of the autumn after a national agent was chosen for a sale expected to top £10 million.
The sale is part of a major reshuffle at Brighton and Hove City Council with staff set to move to Hove Town Hall.
Plans for £9.8 million of improvements to the town hall in Norton Road, Hove, to take the extra staff were submitted this week.
The work would see extra space created on three floors over the entrance creating a ground floor café and extra office space.
A 500 square metre extension of the second floor will also help to take staff set to move from the seafront offices.
The original Hove Town Hall was destroyed by fire in 1966 and rebuilt to its current design by 1974 with extensions adding a registrar’s office, a Citizen’s Advice Bureau and a 1991 tourist centre.
Cushman and Wakefield of London will be national agent for the sale.
Estate agent Phil Graves, of Graves Jenkins, expects King’s House to be converted for “high-end” residential properties on the front of the building with affordable housing at the back.
He added: “It’s interesting because converting from commercial to residential, which would probably be at least a 30 per cent uplift in value, flies in the face of council policy so it will be Brighton and Hove’s planning department deciding future use and value for Brighton and Hove City Council.
“I am also frustrated that the council have not chosen a local agent to handle the sale.
“There are plenty of good quality property firms who would be more than capable.”