Complaint needs to be lodged before police will investigate inappropriate behaviour allegations of Christchurch city councillor

The council's appointed an independent investigator to look into multiple complaints a councillor has been messaging girls as young as 13 with sexually explicit content.

Acting CEO Mary Richardson met complainants last week.

Mayor Lianne Dalziel has known of the allegations since May, and says it's up to the complainants to contact police.

But she says if during the course of the investigation they have concerns - they will refer those to police.