The country’s biggest non-metropolitan district council, by population, has come into being after a merger.
East Suffolk, made up of the former Suffolk Coastal and Waveney district councils, will serve 246,913 people.
A second new authority, West Suffolk, has taken over from St Edmundsbury and Forest Heath councils.
West Suffolk will serve a population of 179,248 and the number of councillors to be elected for both new authorities in May will be halved.
The mergers have taken two years of negotiating and will have fewer elected representatives.
Suffolk Coastal and Waveney have been working in partnership since 2008, sharing an “integrated workforce” and, on its website, East Suffolk council said the two separate councils had saved £16m since 2010.
Dr Christopher Huggins, politics lecturer at the University of Suffolk said