A detective inspector accused of gross misconduct abused his rank to get junior colleagues to gratify him sexually and coerced one of them to perform sex acts in police vehicles and at a police station, a disciplinary hearing was told.
Simon Hurwood was obsessed with the colour of female colleagues' knickers and groomed subordinates into sending him explicit photos and videos, the disciplinary panel heard.
Some of the allegations brought up at the disciplinary hearing related to when he worked in Cleveland Police's Professional Standards Department, based at the force headquarters.
Married Mr Hurwood resigned last month and is not represented or attending the hearing at Middlesbrough Football Club's stadium.
The officer, who joined the force in 1991, faces allegations relating to 21 female colleagues, most of them officers.
John Beggs, representing the force, said: "Their common theme is that of DI Hurwood, over a lengthy period of time, abusing his rank and status to gratify himself sexually with almost always subordinate and vulnerable females."
The hearing was told he relentlessly pursued women, often while on duty and on police premises.
He would quickly get hold of their personal mobile phone numbers, target women with issues in their private life and offload his own troubles to gain sympathy, Mr Beggs said.
Mr Hurwood would then send increasingly flirtatious texts and seek to get explicit photos or videos from the women, the barrister said.
Mr Beggs said one of his "several obsessions" was to seek to identify what colour knickers they were wearing.
Investigations began when an anonymous email making allegations about his conduct towards women was sent to the force's Counter Corruption Unit in January, and he was arrested in March and interviewed about alleged misconduct in June.
He will not face criminal charges due to a lack of evidence.
The first complainant, referred to as Witness A, was a probationer when she worked with Mr Hurwood and she alleged he made sexually inappropriate comments to her.
Mr Beggs said she alleged Mr Hurwood told her: "When we do have sex it will be as if I was gonna rape you because that's what girls like."
The barrister said Mr Hurwood coerced the woman into performing a sex act on numerous occasions, including in police vehicles and in a closed office at a police station.
The woman said she felt she had to go along with it as he was her boss.
Mr Hurwood was to later claim in interview that Witness A pursued him sexually and he denied anything sexual happened at work.
Another woman, Witness H, claimed he groomed her and swamped her with texts, promising to help her career.
The texting ramped up to the point that she felt sick when he contacted her, knowing she would have to reply, the hearing was told.
The subject became sexual as he described what he wanted to do with her at work, and she felt pressured into replying.
She said he persuaded her to send explicit videos and afterwards she felt "prostituted" and dirty.
He would persuade her to take photos in the toilet while at work and would grab her in the office.
Witness H said he would demand naked videos when she got home, of her posing or in the bath.
Mr Hurwood denied any sexual activity with the woman and said the photos were sent at her instigation.
Another woman, Witness I, said he groped her in the office, rubbed himself against her and shared a sexual headmaster-schoolgirl fantasy.
She said: "I feel he's worked me to a point where I have been under some sort of spell."
Mr Hurwood told interviewers there was sexual tension and admitted there were inappropriate emails but said it was Witness I who tried to touch him.
Witness J said she was confused by his flirtatious texts, saying "He was old enough to be my dad", but that she liked the attention and flattery.
This woman said he groped her up her dress, and she said: "I did say, like, no we can't, but I didn't feel strong enough to pull away."
He later coerced her into having sex at work, the hearing was told.
Mr Hurwood later admitted there was a sexual relationship but denied it took place while on duty.
He also allegedly told another colleague "what if I told you I could be your sugar daddy and give you the best sex you've ever had".
He denied making any offensive comment towards her.
Disciplinary hearing chairman Simon Mallett said the panel's ruling would not be before 3pm on Tuesday.