A jury in Hobart has found former Upper House MP Terry Martin guilty of child sex crimes.

Martin was found guilty of unlawful sexual intercourse with a young person under 17 and producing child exploitation material, but the verdicts were not unanimous.

The jury could not reach a verdict on a third charge of indecent assault.

The 54-year-old had denied all charges because he thought the girl was 18.

Martin responded to an advertisement for adult sexual services in September 2009 placed by the girl's mother and pimp Gary Devine.

He paid a 12-year-old girl $600 to perform sex acts and he photographed them.

Martin has been remanded in custody for sentencing submissions today.

It is understood his lawyer Peter Barker has told the court he will seek a non-custodial sentence.

He told the court the former MP poses no risk of reoffending because the medication he takes for Parkinsons disease, which causes hyper sexuality, has been changed.