An elderly man who persistently sexually abused the teenage daughter of his close friends, stopping only when the victim’s mother caught him in the act, has been jailed for four years.

The 71-year-old man, who cannot be named for legal reasons, met the girl through her parents when she was five years old and became a trusted “grandfatherly” figure in her life.

But in what WA District Court Judge Simon Stone today described as a “gross breach of trust”, the older man began sexually abusing the when she turned 13, performing oral sex on her every fortnight for a year at the girl’s home and at his own.

The man’s abuse was almost uncovered in December 2016 when the girl’s father returned home as he was assaulting the victim in her mother’s bedroom.

However, he was able to escape detection after he hid in a wardrobe to get dressed while the girl pretended to get dressed in the bathroom.

Seven months later, in July last year, the man was again abusing the young girl in the same bedroom as they watched television, but this time the court was told the girl’s mother “interrupted” the perverted act.

The mother slapped the offender, who apologised, with the mother recording the conversation.

Prosecutor Nathan Fawkes said the victim did not want her parents to call the police and in “their culture” such things could be dealt with by way of payment, with the parents later demanding $100,000.

Mr Fawkes said the demand for money was abandoned after talking to a lawyer.

In the meantime, the offender did pay the family $10,000 after the victim’s parents said that they would go to the police if he would not pay them the money.

Defence lawyer Seamus Rafferty said his client looked at the victim as a granddaughter but “for whatever reason he effectively started looking at her as an adult”.

“Clearly his moral compass completely and utterly askew,” he said.

Judge Stone said the man emotionally manipulated the girl, including by conspiring with her to keep it a secret from her parents, saying he committed a “gross breach of trust”.

He said the pair formed a close relationship over years but said at some point in time, he came to view her in an “inappropriate way” and “began to abuse her in a very intimate way”.

“You offended against her for your own sexual gratification,” he said.

Judge Stone said while he accepted the girl did not resist the acts “the fact that she did not does not indicate any consent”.

“Your offending is very serious,” he said.

“You only stopped because you were caught by (the girl’s) mother in the act.”

He said in the girl’s victim impact statement, she said the offending had significantly affected her relationship with her parents and had left her with trust issues and feelings of shame.

The man, who pleaded guilty to persistently engaging in sexual conduct with a child under 16, must serve two years behind bars before becoming eligible for parole.

He was made a reportable sex offender.