Samantha Anderson-Graham, of Sudbury, Suffolk, was driving along a country road with her daughter, Tilly, when they came across a terrier in the middle of the road.
Samantha initially beeped her horn to hurry the dog across the road, but when it failed to move, she realised that it did not appear to have an owner.
The mum-of-four then decided to get out of the car and shoo the dog to safety, but when she opened the car door, the terrier sprang into the vehicle and set upon Tilly.
As a horrified Samantha battled to rescue her daughter, the dog - apparently a stray - scratched and bit at the four-year-old, who was left with bloody tooth and claw marks on her face and body.
Some of the marks were less than an inch from Tilly's eye, and she also suffered a puncture wound to her leg, as well as scratch marks on her arms and legs. Samantha was also bitten in the tussle as she tried to protect her daughter.
After the animal had been driven off, Samantha contacted her local police force to report the incident and was shocked to learn that they would not be opening an investigation.
The 38-year-old claims she was told by police officers that they were unable to investigate the attack because the dog was in her vehicle when it took place.