A pastor has been jailed for 10 and a half years for drugging, blindfolding and raping a 13-year-old girl.

David Volmer, 41, pleaded guilty to 12 offences at the West Australian District Court. Volmer, who had been head of the West Australian Prison Fellowship Program, forced the girl to strip naked while blindfolded and then raped her as her father was in the same room, also blindfolded.

The court heard that Volmer offered sexual massage services on the advertising website, Craigslist, to which the girl's father responded. After the first meeting in a park, Volmer later told police he knew the girl was not 16 as her father had claimed but went ahead and arranged a second meeting in a hotel anyway.

There he abused the girl, whom he had drugged, while her father watched. A year later Volmer contacted the father again and arranged another meeting in the girl's house where he abused her again while she was blindfolded and drugged. Her father was again in the room, also blindfolded.

Volmer then arranged a final meeting with the girl where he abused her again, even more seriously.

His behaviour was part of a sexual double life Volmer had been living behind his wife's back, the court heard.

Volmer's defence said that he had tried to apologise but felt the words were "empty and powerless."

"He wants to say it [sorry] over and over again from the rooftops," he said.

As well as being head of the prison program, Volmer was a pastor at ACTS church in Carramar which closed after he admitted the offences.

The church said they could offer "no excuses for such disgraceful and disgusting behaviour."

Presiding over the case, Judge Mark Herron said it must have been a "frustrating and distressing" experience for the "vulnerable and defenceless" girl who had been drugged with amyl nitrate.

The "degrading and humiliating" acts were committed for Volmer's own sexual gratification, he added, while acknowledging that Volmer had expressed remorse, cooperated with police and begun rehabilitation.

Volmer will be eligible for parole after serving eight and a half years of his sentence.