The animal rights group Peta has called for the use of police dogs to be phased out after animals were hit with bricks and burned during riots last month.
Staffordshire PD Vixen was one of several to be injured as disorder swept the UK in the wake of the Southport stabbings.
The charity called for "safer, modern policing technology" to replace dogs.
Police have yet to respond, but in introducing new standards in April, the National Police Chiefs Council said they "rightly place a significant emphasis on the welfare and care of police dogs".
It also paid tribute to the animals, which "dedicate a lifetime of service, working alongside police officers and staff to keeping our communities safe".
In addressing its call to the Metropolitan Police commissioner, Peta (People for the Ethical Treatment of Animals) said "unlike human officers, they did not choose to enlist or put their lives on the line".
Like Vixen, Merseyside Police dogs Ike and Zoe were "hit by bricks thrown by the unruly crowd" in Southport, Peta wrote in the letter to Sir Mark Rowley.
"Over the years, we have also read reports of dogs who have been punched or kicked or whose eyes have been gouged during altercations," it said.
"The risk of injury while working, dogs used by the police are vulnerable because too often their wellbeing comes second to other priorities."
Peta's vice president of programmes, Elisa Allen, who sent the letter, said: "Dogs in Britain's police forces never signed up to risk their lives, but are being battered on the front lines of riots and left to bake to death in hot cars."
The group highlighted the case of West Mercia PD Ivy, who suffered heatstroke and died in 2018 after being left in the back of a police vehicle for more than two hours on a hot day.
A subsequent review found that although the handler had left the engine running to keep the air conditioning on, an extractor fan in the back of the vehicle had malfunctioned, and there was not enough awareness of how the system worked.
Temperatures reached 26C (78.8F) in Worcester on the day the Belgian Malinois cross was found unresponsive.
The police investigation into her death made 17 recommendations, including air conditioning checks on all force vehicles used to transport dogs and formal dog first aid training for West Mercia Police officers.
Hundreds of puppies are bred to be used by UK forces each year, with West Midlands Police alone holding 40 females and producing about 100 puppies annually, Peta claimed.
Police dogs perform a variety of roles, from law enforcement to tracking suspects, search and rescue, and uncovering weapons, drugs or other substances.
On Sunday, West Midlands Police paid tribute to three of its "digi dogs", spaniels which help search for devices such as mobile phones, SIM cars and memory sticks, which can often be important evidence.