The Royal Mail says letterboxes should be a no-go zone for pets after a high court ruled that owners could face five-years imprisonment if their dog bites a postal worker.

The High Court has ruled that dog owners who fail to take steps to prevent their dogs from biting postal workers fingers through a letter box, whether the owners are home or not, could be convicted of an offence contrary to the Dangerous Dogs Act.

Owners could then face a maximum of up to five-years in prison and in response to the ruling the postal service is calling on owners to keep pets away from letterboxes in their home. 

This clarification of the act was made in a case brought by the Royal Mail after a postman lost the tip of his finger when a dog bit him as his hand partially came through the letterbox whilst he was delivering mail.

According to the postal service, the owner had left the dog alone at the address at the time and the dog had not injured anyone before.

The court ruled that the decision applies to postal workers or anyone lawfully visiting the premises, such as someone delivering a free newspaper or distributing leaflets.

The judge said that there will be a short time when someone exposes their fingers to a dog within the property and if the dog injures that person and the owner had allowed the dog to freely roam the house then the owner could be criminally liable. 

The ruling will require dog owners to install letter box cages or otherwise keep dogs away from the front door or face prosecution if injury is caused to a person delivering to the house.

If a conviction was to occur the court must order destruction of the dog, unless the owner proves it is no longer danger to the public.

The court also has power to disqualify someone from owning dogs and order unlimited compensation to the victim.

Royal Mail Group global director of safety, health wellbeing and sustainability, Dr Shaun Davis said: "We know that the majority of dog owners are responsible and will do all they can to ensure their pet doesn’t harm anyone.

"However, even the most lovable dog can be a danger to postal staff. Dogs are territorial by nature and if they feel they need to protect their family, they can become unpredictable."