The Commission of the Promotion of Virtue and the Prevention of Vice, known unofficially as Mutawaa, also vowed to punish the assailants, after an investigation prompted by a YouTube video showing members attacking the man and his Saudi wife.
The video showed a commission agent jump out of his car and attack the Briton and a woman in black abaya cloak outside a supermarket.
The commission said in a statement that the investigation proved its patrol had violated instructions and "escalated" the incident after members spotted the man paying at a female-only cash desk.
The commission said the patrol "had no authority" to question the man's right to pay at the desk, especially after it was clear that his wife was accompanying him, adding that mall security should handle such a situation.
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"The commission apologises to the resident and his wife," it said, insisting the act was an "isolated" incident.
It said that four members involved in the attack were pulled from the patrols service and posted to desk positions in areas outside the capital.
Commission members enforce a strict segregation of the sexes and have traditionally forced women to cover from head-to-toe when in public.
They also patrol shops to make sure they are shuttered during prayer times.