The High Court in Glasgow heard 62-year-old James Ainsworth told two of his female victims: "I'm a police officer, no-one will believe you."
Ainsworth pleaded guilty to seven charges of sexual abuse and one of rape.
The offences were committed between 1965 and 1990 in Ayrshire and Dumfriesshire. One girl was abused in a police house.
He admitted the offences as a second trial against him was about to start.
The first trial had to be abandoned after Ainsworth was assaulted outside court.
Judge Norman Ritchie also placed Ainsworth on the sex offenders' register.