A gas port assembly is provided for supplying or removing one or more gases to a powered electrode in a plasma processing chamber. The chamber has at least one electrode (11) to which an alternating electrical potential is applied in use, the assembly being electrically insulated from the electrode(s). The assembly comprises, a number of dielectric members (15) and a number of electrically conductive members (16). The members are arranged in a stack of alternating dielectric and electrically conductive members. Each member comprises at least one gas pathway for the passage of the gas(es), such that when stacked, the gas pathways are in communication with each other and the gas(es) are able to pass between an outer side of the stack and a chamber side of the stack. The members act as a capacitive divider to reduce high voltages within the assembly.