CPS rape guidance
Dennis William Newall admitted to kidnapping and raping two prostitutes Getty

An Australian truck driver has admitted to kidnapping two prostitutes and forcing them onto his live-in bus where he kept a crucifix-shaped 'raping machine'.

Dennis William Newall, 56, is already in jail for raping a backpacker in Western Australia in 2011 and was given an eight year jail term for raping a Melbourne sex worker in 2002.

On 30 January, Newall pleaded guilty to kidnapping and raping two St Kilda prostitutes on separate occasions in November and December, 2001. He is due to be sentenced at a later date.

The women, who were aged 20 and 27 at the time, did not go to police about the attacks until recently.

Newall told one victim "no one would believe a junkie whore" like her, she told Victorian County Court.

The court heard both women feared for their lives after he lured them into his car, covered their heads and took them to a converted bus in Brooklyn, a suburb in Melbourne.

Newall kept a wooden cross-like structure on the bus and told one woman it was a "sex machine" and he was planning to add a mechanical arm to it.

He asked one of his victims to "rate his performance" after raping her and later requested her phone number.

"I couldn't wrap my head around the sadism and depravity needed to build such a machine," she told the court.

The court heard he forced his son, then 17, to carry out one of the kidnappings. The teenager allegedly leapt out of the boot of Newall's car and covered one of the women's head with a pillowcase while she was sitting in the back seat.

An unknown man was also involved in the other kidnapping.

Defence barrister Shaun Ginsbourg said Newall was remorseful over his behaviour.