Dog attacks remain a "major concern" for postal workers after almost 2,300 incidents were reported last year, new figures show.
The Royal Mail revealed that, although the total number of attacks fell by 8%, there were increases in several areas of the country.
Postal workers bitten by dogs have been left with permanent and disabling injuries, with more than 44 attacks every week despite years of campaigns aimed at protecting employees.
The worst areas for attacks last year were Torquay, Stockport, Oldham, St Albans, Slough, Colchester, Blackburn, Llandudno, Hemel Hempstead and Hull.
Shaun Davis, of Royal Mail, said: "Our research continues to show that attacks happen most often in the summer, so we are continuing our campaign to appeal to customers to help us cut attacks across the UK.
"I am pleased that the overall dog attacks numbers continue to fall, but I am still very concerned that in some postcodes attacks are on the increase. I am appealing to dog owners to think twice when the postman calls.
"People should remember that 82% of attacks happen at the front door or in the garden, so this is not just a Royal Mail issue - many other delivery and utility companies and local authorities face the same problem."
Dave Joyce, of the Communication Workers Union, said: "The failure of some dog owners to control their animals remains a major concern for postal workers and the public.
"Seven postal workers are attacked by dogs every working day of the year, which is unacceptable.
"More and more dog attacks happen on postal workers at the front door or in the front garden and that number is increasing as we deliver more online-purchased parcels.
"The vast majority of our customers and their dogs aren't a problem but irresponsible and reckless dog owners are."
Alan Quinn, from Paisley in Scotland, a postman for 10 years, was delivering to a house with a German shepherd when he was attacked and bitten on his arm, which required hospital treatment and physiotherapy.
He said: "I had been delivering there for over 10 years and the dog was never a problem but, on this day, it got out and jumped on me at the external postbox and bit and tore into my arm and I was screaming for help covered in blood.
"The owner then took me to hospital. I never for a moment expected it.
"I'm not on the route anymore but I am very wary of dogs now - more than before. I'd just ask customers: please keep your dog away from the door, don't have your dog loose in the garden when we are all on our rounds."