The findings reveal significant seasonal peaks of chocolate ingestion cases across the year, most notably on Christmas and to a lesser extent at Easter, as chocolate becomes more accessible within the home.
The risk is because chocolate contains a toxic ingredient called theobromine.
Theobromine is a caffeine-like stimulant which can lead to an upset stomach, a racing heartbeat, dehydration, seizures and, in the most severe cases, death in dogs, the researchers said.
"Dogs love a chocolate treat and at Christmas there are plenty about. Sadly dogs can't eat chocolate safely so people should keep festive chocolates away from pets," said P-J.M. Noble, veterinary researcher at the University of Liverpool.
"If chocolate is consumed, owners should talk to their vet as soon as possible, and ideally be prepared to quantify the amount and type of chocolate consumed," Noble added.
For the study, published in the journal Veterinary Record, researchers analysed 386 cases of chocolate ingestion in dogs from 229 UK veterinary practices between 2013 and 2017.
The study also found that chocolate ingestion was significantly less common in older dogs and that no specific breed is more at risk than others.
In 2016, the UK's Royal Veterinary College warned of the dangers of dogs eating festive cookies, cake or mince pies containing raisins, grapes, pointing out that the fruits can cause kidney failure.