The man was trying to assist police chasing a burglary suspect outside his Berrylands' home but the dog mistook him for the suspect.
The 41-year-old father was treated at Kingston Hospital for deep wounds in his left leg, following the attack on the evening of April 16.
Police explained that the man bore an "extraordinary" resemblance to the burglary suspect who was being chased.
A police spokesman said: "The dog has been assessed and is back at work. This was practically unique and it was unfortunate that he happened to be so similar.
"The dogs are trained to get sight of the person they are after. It was not like the dog had been beyond control."
A man from New Malden was arrested at the scene by police and charged with criminal intent to commit burglary in Berrylands.
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