Dogs owners are being urged to mircrochip their dogs to increase the chance of being reunited if separated.
Nearly half of stray dogs coming into Battersea Dogs and Cats Home are not microchipped one year after it became law for owners to do so.
The animal charity has taken in 934 stray dogs across its sites since the law was introduced on April 6, 2016.
Of these, 480 were chipped, a rise of ten per cent "but still not enough". Failure means reuniting dogs with their owners can be very difficult.
A microchip is a tiny device with a unique 15 digit number that can be used as a scanner and includes the details of the owners.
Stray Pandora, an "energetic and sweet-natured" nine-month-old Staffordshire bull terrier is still looking for a home
The gallery includes strays that have found new owners after being rehomed.
Battersea’s deputy chief executive, Peter Laurie, said: "These pictures show 12 other lovely stray dogs, like Pandora, that have come into our care with no way of tracing their owners.
"Luckily, we found loving new homes for all these dogs, but we continue to see the consequences of owners failing to chip their animals.
"It’s encouraging to see that more of the strays that come to Battersea are microchipped but there are still so many who aren’t.
"A microchip is the size of a grain of rice and is totally painless for an animal – there just isn’t a good reason not to get it done, especially now it’s been law for a year.
"By making a decision not to chip their pet or not keeping the chip’s details updated, the owner is gambling that their dog will never go missing. Unfortunately, dogs run away, escape and get stolen – it’s not worth the risk.
"It’s a simple procedure that could save both you and your pet from weeks of misery and distress."
Nationally 94.5 per cent of dogs are now microchipped compared to 86 per cent in April 2016, an increase of 710,000, It means about 450,000 are not.
If a dog owner is caught without having their pet chipped, they face a fine of up to £500.
Dr Huw Stacey, director of clinical services at Vets4Pets, said the rise in microchipping was "encouraging".
He added: "We’re hoping the anniversary will encourage dog owners to get their dog microchipped if they haven’t done so already."