That area of the main tap should have a packing gland with a nut on top in the area you pointed to with the arrow. If it has, try to nip it up ever so slightly this usually stops it. If not do not attempt to remove it! In the Sydney Water area this tap is the responsibility of the Authority and they replace it for nothing. I wouldn't know if this is the same or not in Melbourne.
As I said don't attempt to change it yourself, it will have to be frozen.