The app, known as Operator Initiated Facial Recognition (OIFR), has already been tested by 70 officers across south Wales and will be used by South Wales Police and Gwent Police.

Police said its use on unconscious or dead people would help officers to identify them promptly so their family can be reached with care and compassion. In cases where someone is wanted for a criminal offence, the forces said it would secure their quick arrest and detention.

Police also said cases of mistaken identity would be easily resolved without the need to visit a police station or custody suite.

Police said photos taken using the app would not be retained, and those taken in private places such as houses, schools, medical facilities and places of worship would only be used in situations relating to a risk of significant harm.

The civil liberties group, Liberty is urging new privacy protections from the government and  privacy group Big Brother Watch has reminded the world plus dog that the no Brit has to identify themselves to police without very good reason.

 Both groups fear unregulated surveillance tech threatens to takes a fundamental right to be anonymous away.