A gross misconduct hearing is underway over whether former PC Luke Chalmers began an inappropriate three-month sexual relationship with a woman he cautioned for assault on a case in June 2017.
He is also accused of having sex with the woman at her house while on duty, using his force-issued mobile phone to text women he met on other cases and using police computer systems to look up their personal details after their cases were closed.
The panel also heard Chalmers made eight searches on an adult video website within 70 minutes while on duty in October 2017.
The 30-year-old - who did not attend the first day of the hearing yesterday (January 28) and reportedly 'has not engaged' with the force's disciplinary process - denied all allegations of misconduct when he was interviewed.
Since the allegations arose, he has resigned from the force.
Liz Briggs, a solicitor acting for Northamptonshire Police, said: "We put forward this isn't simply an officer who acted inappropriately but an officer who clearly cultivated these vulnerable people he'd come into contact with.
"It is our case this abuse of position for sexual purposes falls under serious corruption."
It is alleged that former PC Chalmers used his force mobile phone to text three women he met on cases, where he gave them his personal mobile number and told them 'don't be a stranger'.
It reportedly escalated into a sexual relationship with one of the women and texts read out to the panel showed he drove to her house while on duty for sex. He also sped up the relationship by telling her he was 'moving to Australia soon' and they should 'make the most of their time together'.
When his long-term partner asked who one of the women were, the panel heard, he told her she was a Crown Prosecution Service (C lawyer.
The disciplinary hearing is expected to make a ruling on the case this afternoon (January 29).