An initiative or referendum petition may be amended at any time within ten days after the notification of insufficiency has been sent to the committee of the petitioners by the City Clerk, by filing a supplementary petition upon additional papers signed and filed as provided in case of an original petition. The City Clerk shall, within five days after such an amendment is filed, examine the amended petition and, if the petition is still insufficient, he shall file his certificate to that effect in his office and notify the committee of the petitioners of his findings and no further action shall be had on such insufficient petition. The finding of the insufficiency of a petition shall not prejudice the filing of a new petition for the same purpose.