Section 17A. The mayor or city manager and the members of the city council shall receive for their services such salary as the city council shall by ordinance determine, and they shall receive no other compensation from the city, except that a member of a city or town council in a municipality with a city or town council form of government may receive a salary for serving as a municipal employee of said municipality in lieu of receiving compensation for serving as a member of said council. No increase or reduction in the salaries of mayor or city councillors shall take effect during the year in which such increase or reduction is voted, and no change in such salaries shall be made between the election of a new council and the qualification of the new council. The provisions of this section shall not be applicable in a city under Plan F.