A former Jehovah's Witness elder recently convicted of child sex offences is back working with children from a Melbourne parish run by his father-in-law.

Richard Hill was found guilty last year of the offences against his six-year-old female cousin, who was also in the religion. He was put on the sex offenders' list and fined. The offences happened in 1981 when he was 20.

Hill, a roofing plumber of Doreen with an office in Brunswick, this week maintained his innocence and confirmed he was working with children while doorknocking as part of the Jehovah's Witnesses religious practice called 'proselytizing.'

His wife's father, Ken Hall, is the senior elder at the Plenty Kingdom Hall in outer Melbourne, where Hill now worships. "I am allowed to attend under strict conditions," Hill said. "The police know about that."

Hill appealed his conviction but then dropped the appeal.

"I pleaded not guilty to all charges but we decided not to keep going because of mental stress on my family and the costs – I spent over $100,000 defending myself in the courts. You get to a point where you turn the other cheek and walk away. I am definitely not guilty. It comes down to one man's opinion over another person's opinion."

However he apologised to his victim, Melissa Buchanan, on social media, as she was preparing to tell police what had happened to her as a little girl. "I'm truly sorry Melissa," he told her in a Facebook message. "I know you must be hurt and I'm so sorry for that. Trust is very hard to earn but easy to destroy."

Ms Buchanan, 41, who is no longer in the sect, told police Hill was living in her family home in the northern suburbs in the 1980's and one night after a shower he came into her bedroom dressed only in a small yellow towel and after making her sit on his lap sexually abused her while telling her to be quiet.

Her family, she says, all staunch Jehovah's Witnesses, hushed it up to save face and the church's reputation, and Hill later became an elder.

"He could very easily do to others what he did to me," she says. "I don't know how they can have a convicted paedophile knocking on doors speaking about religion. I just want him to know that I will never forget."