Devoted dog owners made it in time to have their pets electronically tagged yesterday as experts warned it can be impossible to reunite lost dogs with their owners without the technology.

Yesterday’s deadline saw vets on a microchipping mission to ensure the county’s dogs could be traced if lost or stolen.

Owners face a fine of up to £500 if their pet is found without the tiny chip, which carries a unique 15-digit code under loose skin on the back of the dog’s neck.

If a lost or stolen dog turns up, the chip can be scanned and matched to a database – if authorities come across a dog without a chip, owners will be given three weeks to comply with the law, which the Department for Environment, Food and Rural Affairs (Defra) warned had not been universally obeyed.

More than a million of Britain’s dogs were yet to be microchipped by yesterday, said Defra, which also warned owners must ensure they update chips if changing contact details.

Blue Cross in Suffolk said that without the chip, lost family dogs could be taken in as strays by rehoming centres and kennels.

Last year, a fifth of the 143 dogs admitted to the rehoming centre in Suffolk came from dog pounds, or were found wandering the streets.

Seven of every 10 brought for rehoming were not chipped, according to the charity, which said people may now have to prove ownership, and even formally apply to rehome their dog, if it turns up without a chip.

Andrew Gillon, Blue Cross centre manager at Wherstead, said: “While we never know how a pet has become a stray, we see many in good health and really friendly towards people. It suggests many are pets that could be being missed by devastated families.

“Some dogs have even been trained, which means they must have been owned and looked after before they came to us.

“Without a microchip it is sadly impossible for us to trace their owners and get them home.”

Microchipping technology has been in place for about 25 years, and is now compulsory in England, Wales and Scotland – Northern Ireland having introduced a similar law in 2012 – but it does not replace requirements for dogs to wear a collar and tag.

Owners must make sure their pet is fitted with a microchip by the time it turns eight-weeks-old. According to the Dogs Trust 28% of lost dogs were returned to their owners in 2015 thanks to microchipping.