Organisations including Brighton & Hove City Council and the East Sussex Fire & Rescue Service have invited firms and chambers to tender, with the process being managed by Arun District Council.
Advice is being sought on areas including administrative and local government work, adult and child services, education, employment, highways, housing, and licensing.
One head of legal at a participating authority said: “We’ve invited firms we already work with. Each authority will decide whether we continue with current arrangements. But the idea is, if you do it, you pay more than lip service to it.”
This comes after a smaller group of local authorities in the Sussex area previously had to abandon plans for a joint panel due to insufficient volumes of work.