A former police inspector who targeted junior colleagues for sex committed gross misconduct, a panel has ruled.
Ex-Cleveland Police Det Insp Simon Hurwood used "coercive behaviour" and sent thousands of messages to 21 women over a 14-year period.
The force said he had "acted shamefully" and praised the bravery of the anonymous whistleblower.
Hurwood, 53, who resigned in September after 27 years of service, had denied any wrongdoing.
A disciplinary hearing in Middlesbrough upheld eight allegations of gross misconduct and eight more of misconduct.
Hurwood preyed upon younger women who were having problems in their personal lives and had full sexual contact with four of them, the panel was told.
In a statement, one woman described how Hurwood "coerced" her into performing sex acts on him in police vehicles and an inspector's office.
She said she feared she would "probably" lose her job if she reported it.
Another said Hurwood persuaded her to have sex with him in an office while they were on duty.
'Out of control'
Cleveland chief constable Mike Veale said the force would "not tolerate anyone at any rank abusing their position of authority and trust".
He added: "For more than a decade he [Hurwood] acted shamefully and was confronted thanks to a brave individual coming forward and blowing the whistle on him."
A member of the force since 1991, Hurwood went on to work in its professional standards department.
However, he treated it as a "personal recruitment centre" for his own sexual gratification, panel chairman Simon Mallett said.
Towards the end of his time there he "was out of control" in his "unfettered pursuit of young women".
Mr Mallett said his behaviour amounted to "grooming over time".
When he had previously been challenged about his behaviour, Hurwood had "laughed off" allegations put to him and no action had been taken.
The panel concluded he would have been dismissed without notice if he had still been a serving officer and he will be added to a list barring him from rejoining the profession.
The former policeman was not represented nor present at the hearing.
When questioned at the outset of the investigation, he said sex with one complainant had been consensual while other allegations were "cruel nonsense".
In March, Hurwood was arrested for sexual assault offences and suspended from duty.
However, it was decided there was insufficient evidence to pursue a criminal prosecution or misconduct in public office charge.