Ian Hooper told the little girl to get on his mobility scooter before touching the outside of her underwear as she left a Mildura primary school in December 2019.

The 65-year-old started riding away with the girl before a school parent saw what was happening and confronted Hooper.

In jailing him for a maximum of six years on Friday, Victorian County Court Judge Gregory Lyon condemned the man's actions as "the stuff of nightmares for all children's parents".

Hooper lived 350 metres from the school and told police he'd wanted to do this "for a little while".

He also said he'd wanted to play with the child's vagina and picked a little girl because he "couldn't get a big one".

"The community must be grateful for the vigilance and tenacity of the witness who saw you and confronted you," Judge Lyon said.

Hooper was angry about what happened to him after being caught with the girl, according to psychological reports.

He also appeared to see nothing amiss with stealing the child but went on to begrudgingly admit his actions were wrong.

Hooper used a mobility scooter at the time because of an acquired brain injury following two earlier strokes. He also likely had an undiagnosed intellectual disability.

He pleaded guilty to abducting a child under the age of 16 for sexual purposes and sexually assaulting a child under the age of 16.

He must serve at least four years' jail before becoming eligible for release on parole and has already spent 227 days in custody.

Australian Associated Press