PC Andrew Beech restrained Samantha Chadwick for 11 minutes, causing her to cry in pain.
When witnesses tried to intervene he told them to “back off” before saying they should tell police it had only been a “verbal domestic” incident, today's meeting at the force’s headquarters in Wakefield heard.
West Yorkshire Police chief constable Dee Collins, who chaired the hearing, said she was “extremely concerned” by Beech’s conduct, especially given that he would have known that domestic violence was “one of the force’s key priorities”.
“His actions have certainly brought discredit to the police,” she said.
She said she would have dismissed him for gross misconduct if he had not resigned from the force last month.
Beech, who had been a neighbourhoods officer for West Yorkshire Police in Calderdale, had been off-duty and out drinking with Ms Chadwick, his then-girlfriend, on September 7 last year.
Detective Inspector Mark Truelove, of the Professional Standards Directorate, said the couple were in the Walkers Arms pub in Golcar, Huddersfield, when they began arguing about Ms Chadwick’s daughter.
Beech was heard saying he didn’t care whether her daughter was found dead. Ms Chadwick pushed him and a scuffle ensued.
Beech grabbed her wrist, pulling it behind her back and pinning her to a table for 11 minutes.
Det Insp Truelove said: “When witnesses tried to intervene, Mr Beech told them to back off.”
Ms Chadwick was “crying and visibly shaken”, and had been left bruised, he said.
The police were called and both Beech and Ms Chadwick were arrested.
In a police interview, Beech had argued that his restraining of Ms Chadwick had been “lawful, justified and proportionate”.
But he was charged and later found guilty of assault by beating at a trial. Huddersfield Magistrates’ Court fined him Â£100.
No further action was taken against Ms Chadwick, who is no longer in a relationship with Beech, Det Insp Truelove said.
Beech did not attend the hearing but had admitted gross misconduct in writing, saying he wanted “to apologise to the public of West Yorkshire”, Miss Collins said.
Members of the press and public wanting to watch the proceedings today had to do so via a video link from Havertop police station, in Normanton.