Within thirty days after the publication of any ordinance duly passed by the Council, a petition may be presented to the Council protesting against such ordinance continuing in effect. Said petition shall contain the text of such ordinance and shall be signed by registered electors of the City, not less than fifteen percentum of all votes cast for Mayor at the last preceding election at which a Mayor of the City was elected, but in no case less than three hundred. Said ordinance shall thereupon and thereby be suspended from operation, and the Council shall immediately reconsider such ordinance.
If the ordinance be not entirely repealed, the Council shall submit the question of whether or not it shall become effective to a vote of the electors of the City. The procedure in regard to such petition of protest and referendum shall be the same as hereinabove in this article provided for the initiative and referendum of a proposed ordinance, with such modification as the case may require.