PC Jonathan Marsh was called to a clinic in Atlanta Boulevard on November 13, 2022, by a man who said someone was damaging his surgery sign.
While trying to find the suspect, PC Marsh mistakenly identified Rasike Attanayake, who had phoned 999, as the culprit.
After bundling him to the ground PC Marsh punched him to the back of the head.
The medical worker was handcuffed and put in the back of a police car, before the officers realised their mistake and de-arrested him.
Marsh, from Canvey Island, was found guilty of common assault and was given a 12 week suspended sentence last April.
On Monday (March 24) a Met Police misconduct panel decided to dismiss PC Marsh without notice.
Footage showed PC Marsh using force to arrest a man even as he tries to suggest he is not the suspect (Image: IOPC) Ch Supt Stuart Bell, in charge of policing in Havering, Barking and Dagenham and Redbridge, said: “All police officers know they will be held to account for any use of force, and any use of force must be reasonable.
“On this occasion, PC Marsh went beyond the level of force necessary and it is right that he has to face the consequences of his actions.
“I would like to apologise to the victim of the assault. This incident should not have happened and it is a matter of profound regret that an innocent member of the public was injured in this way.”
Footage released by the Independent Office for Police Conduct (IOPC) showed PC Marsh walking towards Mr Attanayake after a colleague tells him on the radio that he was a suspect.
PC Marsh then hits Mr Attanayake on the head, handcuffs him and asks him to “get on the f****** floor now”.
Mr Attanayake is seen pleading with PC Marsh all this time, suggesting he is the one who called the police and demanding “please can you not do that?”.
PC Marsh will be added to the barred list held by the College of Policing.