A Queensland man has been fined for engaging in a sex act with an underaged girl, forced into prostitution by her mother.

A Brisbane man has been fined $1500 for engaging in a sex act with a 15-year-old girl forced into prostitution by her mother.

District Court judge Richard Jones imposed a “very lenient” sentence on the man, 63.

The man hadn’t solicited the act in October 2010 and had initially thought it was the girl’s mother he was with.

The mother, a prostitute from Thailand, had told her long-standing clients the girl was her 19-year-old sister or cousin.

The girl was living with her grandparents in Thailand when her mother brought her to Australia for a holiday in 2004.

During the six-week stay, the nine-year-old girl was taught massage, masturbation of men, and oral sex.

Two years later, the mother brought the child to Australia permanently to work as a prostitute out of their Runcorn house, in Brisbane’s south.

The girl worked before and after school, and was abused or starved if she complained.

“It is a case that is almost impossible to comprehend for normal people,” Justice Jones said.

“That a mother would, in such a perverse way, corrupt a young daughter from such a very early age.”

The girl, now 19, went to authorities in 2011.

During a house raid, police found photos and more than $200,000 cash in a safe.

The man had been seeing the girl’s mother for five years but never knew her daughter was acting against her will.

Police believe the threats were delivered in front of clients in Thai, and the teen never let on.

The man pleaded guilty and had shown remorse and shame, the court heard.

Justice Jones didn’t record a conviction, so the man can visit his son who lives in the United States.

“I have treated you very leniently, so suggest you don’t come back to this court again,” he said.

The mother was sentenced to nine years in jail in 2013 for child trafficking and will be eligible for parole in three years.