The council has a commercial property portfolio which brings in £8m per year in rent and has over 10,000 acres of farmland.
It says the volume of work has increased so much that it can no longer be handled in-house.
Peter Busby, Thomas Eggar Church Adams' commercial property partner refuses, to say how much the work is worth, but says it is a significant win.
Busby says: “We will have three partners and five other fee-earners working on the account, and although they will not be doing it 100 per cent of the time, we do expect it to make up a substantial amount of their work.”
The firms will work in partnership with the council, and there will be secondments of staff both ways.
Claer Lloyd-Jones, solicitor to Brighton and Hove Council, says: “We selected Thomas Eggar Church Adams and Cripps Harries Hall to deal with the extra workload and bring experience in aspects of substantial commercial property transactions.”
She says the firms beat off stiff competition, but refuses to name the other firms.