If by action of a majority of council, or if fifteen percent of the registered municipal electors present to the municipal election commission a duly executed petition on which none of the signatures is more than six months old, in which an election is sought to change the number of council members to a number authorized by the form of government under which the municipality is then operating or to change the method of election of council members, then the municipal governing body shall call a referendum not later than ninety days nor earlier than thirty days after the petition has been certified and delivered to the governing body by the municipal election commission. A petition must be certified as valid or rejected by the municipal election commission within sixty days after it has been delivered to the commission. There may be only one question framed by the municipal governing body for the referendum in a format similar to that provided by § 5-5-40, and no other election on the same question may be held for two years after that time. If more than one petition is received before publication of a notice of special election, the change sought in the petition bearing the highest number of qualified signatures must be submitted on the ballot. A change receiving a majority of the votes cast is effective at the next general election of the municipality.