A new party may be added, on motion of the plaintiff by order of the court at any stage of the case as the ends of justice may require. The motion, accompanied by a properly executed proposed amended complaint, must be served on the existing parties as required by Rule 1:12. If the motion is granted, the amended pleading accompanying the motion will be deemed filed in the clerk’s office as of the date of the court’s order permitting such amendment and all the provisions of Rule 3:4 apply as to the new parties, but no writ tax, clerk’s fee or deposit for costs is required. All defendants must file pleadings in response thereto as required by these Rules unless otherwise ordered by the court.