A Melbourne man's sexual abuse of his stepdaughter betrayed her trust "in the most despicable way" and he must be punished with prison time, a judge says.

The man, who turns 85 on Wednesday, has been taken into custody ahead of a sentence hearing next week.

County Court Judge Frances Hogan described the man's abuse of the girl, when she was aged between 10 and 14 in the early to mid-1970s, as "insidious" and occurring with "hideous regularity".

The man admitted the abuse earlier this year, pleading guilty to three indecent assault charges and one of gross indecency, but the judge said it came late and she saw little evidence of remorse.

Now in her 50s, the victim was in court to face the man she once considered her father, and who had made her feel special, calling her princess and angel.

The abuse began when he would drive her to a local shopping centre and sit her on his lap to steer the car around the empty car park on Sundays for two years.

He first touched her over her clothes, then under. The abuse escalated when she was 12, beginning when she went into his bedroom to ask for money to buy lollies.

The man pointed to loose change on his dresser and told her she could have it "if you just stand there" while he touched her, later progressing to forcing her to perform oral sex

It occurred regularly until she was 14.

If she wanted money or clothing he would look up and down her body and she knew what was expected, prosecutor Damien Hannan said.

"She was lured into much of this by feeling special, by being rewarded and by being threatened - it was to be kept a secret. And it was," he said.

The girl told her mother about the abuse when she was 12, but she was not believed and was instead grounded for two weeks.

She kept quiet for decades after that, before telling her brother, who confronted the man.

"I know I've done wrong but I can't change things," he replied.

It took another decade before she went to police.

The man's lawyer, Kellie Blair, said he was suffering and at a time when he should be loved, cherished and surrounded by family, "he has none of that".

She said the man had cognitive difficulties, suffered depression and had previously attempted suicide.

Ms Blair called for a suspended sentence, adding that any prison term could be a life sentence.

Judge Hogan said prison was the only appropriate option.

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