A police officer accused of raping a teenage girl told a court she sexually assaulted him but he was too "scared and embarrassed" to report it.
PC Declan Gabriel, 28, who has begun giving evidence at his trial, is also accused of two counts of sexual assault and misconduct in public office.
A jury at Northampton Crown Court was told he forced the 17-year-old girl into an oral sex act in an unmarked police car parked in a lay-by.
PC Gabriel denies all the charges.
The court was told the Northamptonshire Police officer was on duty in a single-crewed vehicle when he attended an incident in Hunsbury, Northampton, in the early hours of 21 September 2015.
The alleged victim had been thrown out of home by her mother and spent two hours with PC Gabriel, apparently as he tried to help her find somewhere to stay, the prosecution told the court.
PC Gabriel told the jury he had pulled in to the lay-by near Northampton Crematorium and had got out of the car briefly to stretch his legs.
On his return he said his underwear had become "extremely uncomfortable" and claims the teenager sexually assaulted him while he was readjusting his clothing.
The trial previously heard the teenager, who cannot be named for legal reasons, told a social worker the next day that PC Gabriel had "forced himself on her".
PC Gabriel said he immediately drove back to the police station after the incident and that it had been his "full intention" to report it but was "scared" that his colleagues would have ridiculed him.
He also told the court how he had been under stress at the time after being badly affected by recent cases he had dealt with, including a suicide.
The trial continues.