All the signature papers shall be filed in the office of the city clerk as one instrument. Within five (5) days after the filing of the petition the city clerk shall ascertain by examination the number of electors whose signatures are appended thereto, and whether this number is at least ten percent of the total number of electors who cast their votes at the last preceding regular municipal election. If he finds the petition insufficient or irregular, he shall at once notify all the members of the committee of sponsors of that fact in writing by mail, certifying the reasons for his finding. The committee shall then be given thirty days in which to file additional signature papers and to correct the petition in all other particulars. If at the end of the period the petition is found to be still insufficient or irregular the clerk shall file the same in his office or shall notify by mail each member of the committee of that fact. The final finding of the insufficiency or irregularity of a petition shall not prejudice the filing of a new petition for the same purpose, nor shall it prevent the council from referring the measure to the electors at the next regular or any special election, at its option.