Kane Cameron, now 21, was sentenced at the County Court of Victoria on Friday.

He pleaded guilty to one charge of using a carriage service to procure a sexual act with a person believed to be under 16 between, September 22 and October 5, 2017.

The court heard the 13-year-old girl told her father about Cameron's messages and the father took over and continued messaging, pretending to be his daughter.

Cameron messaged the father repeatedly asking to meet for sex, believing he was messaging the 13-year-old girl, and he sent an image of his penis.

The father reported Cameron to police and he was arrested in December 2017.

Judge Michael Tinney said Cameron's 'manipulative', 'inappropriate' and 'disgusting' messaging was persistent, even after the fact he was reminded of the girl's age multiple times in the father's messages and was told his requests were illegal.

"This was serious criminal conduct," he said.

"There was harm done. I am very glad that the father of this young girl had schooled his daughter as to what to do if there was ever any concerning online conduct and I am equally glad she informed him.

"You are lucky those things occurred because had they not, you may well have met up in person."

The court heard Cameron had an intellectual disability and a serious medical condition and he had shown an inability to understand the seriousness of his conduct.

Judge Michael Tinney said he took this into account, in addition to Cameron's youth and the fact he had no criminal history.

He said Cameron had reasonable prospects of rehabilitation, but he was guarded because Cameron had shown no insight or provided any explanation for the offending, given he denied an attraction to children.

In his extensive sentencing remarks, Judge Tinney said the offence usually warranted a term of imprisonment, but this was an unusual case given Cameron's young age, lack of priors, poor physical health and mental impairment.

"Prison is always a disposition of last resort," he said.

Cameron was convicted and sentenced to a two-year community corrections order.

He will be required to complete 150-hours of unpaid community work, undergo supervision, treatment and rehabilitation and return to court for judicial monitoring.

He will also be assigned a disability justice worker and will undergo assessment and treatment regarding sexual offences.

"This case shows how prevalent this crime has become," Judge Tinney said.

"Social media platforms are not without risk, especially when there are people like you online.

"There must be a strong message sent to adults who use the internet for their own warped sexual purposes as you did."

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