The Control of Dogs Order 1992
Wearing of collars by dogs
Every dog while in a highway or in a public place must wear a collar with the name and address of the owner inscribed on the collar or on a plate or badge attached to it.If your pet does not have a collar when out in a public place, the dog may be seized by the police and treated as a stray. Also the owner, or any one in charge of the dog and permitting him to be in a public place without a collar, will each be guilty of an offence and may be prosecuted and fined.
If your dog does stray, you should immediately contact your local dog warden (through the Environmental Health Department at your local council) and the local police station. The Environmental Protection Act 1990 allows for your dog to be seized and sold or destroyed if unclaimed after a seven day period. Sadly, dogs are often destroyed because their owners cannot be traced If a dog is microchipped with his own unique identification number registered on a national database,this will help your dog to be returned to you very quickly and save the loss of a much loved pet.
For full infomation on the Law & your pet - http://www.defra.gov.uk/animalh/welfare/domestic/dogs.htm