Royal Mail has urged people to keep their pets under control after revealing that the number of dog attacks against postal workers increased by 8% over the past year to more than 3,300.
Around nine postmen and women are attacked by dogs every day, some leading to a permanent disabling injury.
The postal group said the number of incidents remained "unacceptably high", ahead of new legislation making it possible to prosecute dog owners for attacks on private property.
Royal Mail chairman Donald Brydon said: "We know that most dogs are not inherently dangerous, however, even the most placid animal can be prone to attack if it feels its territory is being threatened.
"Our first priority as an employer is to ensure the welfare and safety of our people who provide a valuable service to our customers.
"We appeal to owners to keep their pets under control, especially if they know their pets have a territorial nature. It can also be simple things that help - for example just making sure the dog is kept inside when the postman calls."
Dave Joyce, the Communication Workers Union's health and safety officer, said: "It is so important for the safety of all postmen and women that dog owners ensure their animals are secure, particularly if opening the door to sign for a parcel.
"The change in the law now means there will be tougher penalties and prison sentences for irresponsible dog owners.
"We welcome this as for too long, postal workers who offer a first class service have been subjected to reckless dog ownership leaving them vulnerable at work and unprotected when a dog attack occurred."
Royal Mail today launched a Dog Awareness Week, including a special postmark on letters, in a bid to raise awareness of the problem.