Prime Minister Chris Hipkins has described the incident as horrific and utterly unacceptable.
Speaking to the AM Show, Hipkins said the photos of the girl in blood-soaked pants and nursing a gash on her head would leave any parent heartbroken.
The young girl was enjoying a meal with her classmates at the McDonald’s when two girls at another table are believed to have “mistakenly” thought they were being laughed at.
“One of the girls proceeded to approach the table, demanding an apology from my sister, assuming they had been mocking her, despite their genuine intentions of having fun,” the victim’s sister told the Herald.
She said her sister would never want to upset anyone and is not the type to engage in fights or “rebellious behaviour”.