Following a series of vicious attacks on children by pit bull terriers, MPs passed the Dangerous Dogs Act 1991.

It banned the breeding and sale of pit bull terriers, Japanese tosas, fila brasileiro and dogo argentino.

To legally own one of these dogs, a certificate of exemption is required but one is only granted when a dog is neutered, insured, and has a transponder implanted beneath its skin.

They must also be muzzled in public places and be led by a person over the age of 16.

The Department for Environment, Food and Rural Affairs (Defra) has set out plans to make it compulsory for all dogs in England to be microchipped from 2016 and extend laws governing dog attacks to cover incidents on private property.

Officials estimate around 210,000 people are attacked by dogs in England every year.