"Extremely distressing" attacks on guide dogs by other dogs are on the increase, topping more than 100 a year, according to a new study.
Figures published in the online journal Veterinary Record reveal that between 2010 and 2015 there were more than 629 attacks - an increase of three per month in 2010 to 11 per month last year.
There are currently more than 4,900 working guide dogs in the UK, providing support and mobility for blind and partially sighted individuals.
James White, Senior Campaigns Manager for the UK charity Guide Dogs, said: "Attacks on guide dogs are extremely distressing for their owners.
"Not only is the attack itself traumatic, but if the dog has to stop working as a guide dog afterwards, then their owner may find it impossible to leave home on their own."
Handlers have reported feeling upset, shaken and anxious after an incident - with 87 people left with injuries of which 59 were guide dog owners and 41 needed medical attention.
Of those animals attacked more than three quarters of guide dogs were working in harnesses at the time.
"The guide dog harness is designed to be visible and should have been apparent to the owners of aggressors who were present," the report states.
"It is feasible that a proportion of these attacks could have been avoided if the aggressor was put on a lead when the owner saw the guide dog in harness."
More than 43% of the animals injured required vet treatment at an estimated cost of £34,514.30.
The most common injuries include puncture wounds, with Staffordshire bull terriers or related breeds reported as the aggressor on 26.4% of occasions.
Attacks were described as being unprovoked in 19% of cases, caused by the aggressor dog in 22% of instances, and caused by a lack of control in 29% of cases. With the owner of the aggressive animal reported as being present in 77% of incidents.
As a result of the attacks more than 20 dogs were withdrawn from the Guide Dogs programme - 13 of which were fully qualified and working with owners - resulting in a £600,000 cost to the charity.
Under the Anti-Social Behaviour, Crime and Police Act passed in 2014, a dog attack on a trained assistance dog will be treated as an aggravated offence.
This means prison sentences of up to three years could be handed to the owner of the attacking dog.
Mr White added: "We were delighted when, in May last year, a new law came into force introducing tougher sentences for owners whose dogs attack guide dogs.
"We had also campaigned for a new law introducing compulsory microchipping for all dogs, which comes into effect this April. We hope these new laws will act as a strong deterrent.
"We are now monitoring how police forces and the courts will use their new powers."
The authors of the study say it is not clear if the rise in attacks is because of a real trend or because of an increase in people reporting them.
But they found that more than 54 dogs were attacked more than once during the study - with 46 attacked twice, seven dogs attacked three times and one dog attacked four times.