Iain Cocks, 51, had sex in cells and a staff room during an illicit affair with an inmate lasting almost two years at Wakefield's New Hall Prison, West Yorks.
The disgraced officer used "gross abuse" of his "position, authority and trust" to carry out the "campaign of inappropriate behaviour", Judge Simon Phillips QC told him as he was given a four year custodial sentence.
Judge Phillips QC said: "The offences involved a persistent and grave breach of trust on your part."
Cocks, who had 20 years of service in the prison system, was convicted of two offences of misconduct in a public office and one count of sexual assault following a seven-day trial at Leeds Crown Court.
He committed the offences between June 2015 and May 2017, the court was told.
The offences included asking one of the women to act out the title of the porn film Debbie Does Dallas during a game of charades.
The prisoner had been given a 'red band' status which allowed her more movement around the prison which Cocks had exploited, the court heard.
The prosecutor said the defendant began "testing the water" by asking her if she was looking at his crotch.
Cocks touched the woman inappropriately as she bent over a washing machine in the laundry room.
They had sex for the first time against a washing machine in June 2015.
Cocks also went to her cell at 6am on New Year’s Day 2016 and had sex with her.
The prosecutor said when prison authorities became suspicious, Cocks told the woman not to tell anyone about their relationship.
He had unprotected sex "six or seven" times with the first victim in a "clandestine relationship", the court was told.
Cocks engaged in inappropriate behaviour with the second inmate when she was moved onto the same wing.
Mr McKone said Cocks told the woman it was “like walking down the aisle” when he first escorted her onto the wing.
He also asked the woman to wear make-up for him and told her it was "difficult not to fall in love" with her.
He stopped when she said to him: “Don’t you think I am vulnerable?”
During the trial he admitted having sex with a third inmate after she was released from the prison on licence.
Cocks told the court how he took her back to his home while his wife was working a nightshift at the prison where they both worked and had sex with her in the spare room.
The jury took just over four hours to reach unanimous verdicts on the misconduct charges and Cocks was convicted of the sex assault charge by a majority of 11-1.
During the sentencing hearing on December 13 at Leeds Crown Court, prosecutor McKone read summaries of victim impact statements.
One of the victims said the relationship affected her progress in prison because he made her feel she would be alone if moved to another prison.
She said Cocks made her feel like he was "her everything" and has been paranoid and "fears being recognised" after media coverage of the case.
The other victim said he would tell her she looked beautiful and make remarks about how she would put on makeup to "impress him".
The victim said he had carried out a "campaign of inappropriate behaviour towards her".
She felt she could not say anything because he was "well liked by other prisoners" and she would "not be believed".
The victim came forward after a fellow inmate had confided in her that he had done the same to her.
Rebecca Stevens, defending Cocks, said he had suffered from anxiety and depression.
She said his character should be taken into account due to the lengthy service he had given.
Sentencing Cocks to four years imprisonment, Judge Simon Phillips QC said: "You used your position to seek to exploit two female prisoners.
"It was a grooming exercise over a number of weeks.
"The fact you were able to persist in this misconduct is attributed to your knowledge of the system.
"You used gross abuse of your position of authority and status."
Cocks was also made subject to an order banning him from any contact with the victims in the case.
He appeared via video link from HMP Manchester in a black and t-shirt.
Cocks sat motionless throughout the sentencing.
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