The police watchdog is investigating footage of a man who appeared to have a seizure while being restrained.
A video of the arrest in Tower Hamlets, east London, which was shared on social media, prompted accusations of police “heavy-handedness”.
Younass Dentahar, 38, claims officers used “unnecessary force” after repeatedly asking him to move his car.
The Independent Office for Police Conduct (IOPC) has launched an investigation.
Footage of the incident, which was caught on body-worn video, shows Met Police officers trying to handcuff the man as he struggled to escape.
A woman can be heard screaming “he’s dying” and “he can’t breathe”.
Later, the man appears to be having a seizure as officers continue to restrain him.
Mr Dentahar was arrested on suspicion of obstruction of the highway, assaulting police and resisting arrest following an incident in Abbott Road, Tower Hamlets on Tuesday,
He has been released while inquiries continue.
Mr Dentahar told the BBC he explained to police that he could park on a single yellow line in the area after 17:30 BST and that his child had a disability.
But after arguing, he claimed he was set upon by three officers,
“The police treated me really bad and humiliated me in front of my children. They handcuffed me for no reason and didn’t explain anything,” he said.
“I used to trust the police but I don’t think they did their job right.”
“I have a cut on my head where they hit me with handcuffs. There was three of them on top of me and I stopped breathing.”
The Met previously said Mr Dentahar was asked to produce his driving licence or move his vehicle, then given a “five stage warning”, before being arrested, which he then resisted.
It later said a referral was made to the IOPC which had now declared it an independent investigation.
During a Home Affairs Select Committee hearing on Wednesday, chairwoman Yvette Cooper called the footage “extremely disturbing” and urged Met Commissioner Cressida Dick to “look closely” at referring the case to the IOPC.