aggressive dogs attacking other dogs

If a person is attacked by an aggressive dog, action is taken and rightly so. When an aggressive dog attacks other, placid dogs, where can you turn to for help? Three years ago, my, then, 10 year old Lab was attacked by a dog who had already attacked other dogs, 5 to my knowledge. I lodged a complaint but nothing was done
This morning, the very same dog attacked my other 12& a half year old Labrador, who, like the first incident, was completely innocent, just sniffing the grass. Whenever you ring to complain, you are passed from Police to Local Government Council, who dont neccessarily have a dog warden. Please support me in this if you are a responsible pet owner, or someone who cares. We need a definite point of contact and action taken against irresponsible dog owners. To be allowed to attack numerous dogs, without a proper authority to insist on the wearing of a lead and/or muzzle, is long overdue.