The term councillor is both -it denotes a member of a council and can be used as a form of address. There is no destinction between an elected or a co-opted councillor. Given that a parish council is the lowest level of local government, many feel that it is less formal than other levels of council. It may be therefore that the less formal the form of address, the better. Ultimately it is for the members of a particular council to determine the way they address each other.