Steven Walters, 48, pleaded guilty to two counts of sexual assault at Stafford Crown Court in September.
Chief Constable David Thompson said the case represented "one of the worst violations of policing integrity I've ever seen".
Walters was also found guilty of gross misconduct at a disciplinary hearing on Monday and dismissed from the force.
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The crimes took place between February and April 2015.
Walters, who was based at Sutton Coldfield, approached a woman in her 20s, who he offered a lift home in his patrol car in the early hours.
After a colleague asked the woman "what she was doing at that time of night in that dress", Walters placed his hand on her thigh when she was in the car, leaving the victim feeling "creeped out".
In the second assault, the court heard he touched the victim under her skirt in her own home while her children were in other rooms.
He attempted to kiss her face and neck, and also asked to be taken to a bedroom.
Sentencing, Judge Paul Glenn said Walters had shown no remorse, adding: "The public are entitled to have faith in police officers and to trust them in the discharge of their powers and responsibilities.
"You exploited that trust and you have brought disgrace on yourself and indeed the force you served."
Derrick Campbell, from the Independent Police Complaints Commission, praised the victims for their "courage and bravery" in reporting his crimes.
"[Walters] completely abused his position of trust by targeting and taking advantage of vulnerable women for his own sexual gratification," he said.
A West Midlands police officer who admitted sexually assaulting two women has been jailed for four years.