The county council is set to save money when its legal department merges with another local authority.
East Sussex County Council and Surrey County Council, which serve a population of more than 1.5 million people, are to join forces to create a single legal service.
The two local authorities say the move will allow them to share expertise and create centres of excellence.
ESCC added that the move would help to reduce cost and protect frontline council services.
The 130-strong legal team will be based at the two existing sites at Lewes and Kingston-upon-Thames.
Philip Baker, assistant chief executive at East Sussex County Council, said: “This is a great opportunity which will enable us to meet the challenges ahead.
“The new single service will allow us to tap into the wider pool of staff members with specialist expertise that comes from an expanded team.
“This is about more than two teams joining together; it is about building a stronger service that enables both authorities to help reduce cost across the public sector, helping councils to protect frontline services.”
While both county councils will benefit from the enhanced service, the new team will also work closely with both existing and new public sector partners to provide what the local authorities described as ‘a first class, one-stop legal service’.
Ann Charlton, director of legal and democratic services at Surrey County Council, told the Observer: “This is a great opportunity to build a stronger legal team to support the work of our two county councils and the residents and businesses they serve.
“As well as our primary work with the two authorities, the move will put us in an even better position to work with a wider range of public service partners.”