If a dog has attacked a person or animal, it is a police matter and you should contact them directly. Call 101 (or 999 in emergencies only).
If you are concerned that a dog is dangerous let us know. Try to give as much information as possible about the dog - breed, colour, location etc.
Owning a dangerous dog
Specific breeds of dog are banned from the UK. It is an offence to own an unregistered banned dog.