Pet owners have been warned not to feed their dogs and cats chocolate, after a new study revealed that potentially fatal poisonings spike during the Christmas period.

More dogs are intoxicated by eating chocolate in the week prior to and fortnight following Christmas than any other time of the year, according to research by experts at the University of Liverpool. The study is the latest evidence which highlights the dangers of feeding animals food intended for human consumption.

Between November 2012 and May 2017, vets in the UK saw over 1,700 dogs feared to have eaten chocolate. More than a fifth of those required further treatment for symptoms such as vomiting.

Dogs were found to have eaten chocolate bars, gift selection boxes, Santa figurines, advent calendars, chocolate oranges, tree decorations and Toblerone bars.

The team at the University of Liverpool made their findings published in the journal Veterinary Record by assessing veterinary records across the UK.

Chocolate is toxic to dogs and cats because it contains methylxanthine theobromine, a substance present in cocoa beans.

"Even small amounts can cause agitation, hyperexcitability, tremors, convulsions and problems with the heart," Seb Prior, senior vet at the Blue Cross pet charity, told IBTimes UK.

As little as 500g (1.1lb) of chocolate can kill a small dog if they are left untreated, according to the PDSA. Animals can also experience seizures, an increased heart rate and, in severe cases, suffer kidney failure and death. Signs that a cat or dog has eaten chocolate also include excessive thirst, vomiting, diarrhoea, and restless behaviour.

"As a general rule the darker the chocolate, the higher the levels of theobromine become. It really is best to avoid your pets getting access to any sort of chocolate," warned Prior.

"Small amounts of some chocolate have the potential to make them feel sick, and as different chocolates contain different amounts of theobromine, it's best to seek veterinary advice if your dog or cat gets some.

"White chocolate does not contain enough theobromine to cause toxicity, but it's usually rich and fatty compared to what our pets are used to and can cause gastrointestinal and abdominal problems as a result. Avoid putting any chocolate on or under the Christmas tree, as the temptation might be too great for our four legged friends," he added.

The effects of chocolate poisoning appear within four hours, and can last up to 24 hours.

Although cats are not naturally attracted to chocolate, pet owners have been known to coax them into eating it.

"Despite cats being more sensitive to the toxic effects of chocolate we actually see fewer cases, probably because cats generally don't have the same ability to taste sweetness," said Prior.

Earlier this year, the PDSA dog charity warned pet owners to keep Easter eggs out of reach of pets after a dog nearly died.

A separate study involving 2,000 dog owners commissioned by revealed that one in eight owners will give their pet unsafe treats during Christmas, including mince pies, chocolate, bones and cheese, SWNS reported.