The father, 63, whose name cannot be published to protect daughter's identity, was convicted of "intentionally procuring a child under 14 for unlawful sexual activity" and for "inciting" and "encouraging" this activity to take place.

The man had pleaded not guilty, claiming that - although he was aware of the wedding - he had not consented to it and did not know about or consent to the sexual intercourse.

But, on Wednesday, Judge Deborah Sweeney convicted him on both counts following a two-week judge alone trial in the Downing Centre District Court.

Judge Sweeney found that, seeing his daughter had reached puberty and was becoming interested in boys, the father decided that the 12-year-old should get married because he believed that, under his religion, having sex outside wedlock was a sin.

She found that that when a then 26-year-old overseas student approached the father at a mosque and indicated that he was interested in his daughter, the father arranged for the pair to swap phone numbers and permitted phone calls and text messages over the coming weeks.

When a "relationship" developed between the pair and the student indicated he wished to marry the 12-year-old, the father not only consented to the marriage but organised for the Islamic wedding ceremony to be held in his home.

The judge found that, afterwards, the father consented to and in fact encouraged the pair to have sex by allowing his daughter to go to live with her new "husband", including spending their wedding night in a local motel.

When the pair came to stay at the father's home, he set up a room so they could sleep together, and told his daughter that she should not use any form of contraceptive pill nor allow her "husband" to use a condom.

They had sex twice while at his home, on two single mattresses pushed together at the father's direction, Judge Sweeney said.

The father believed his daughter was old enough to decide if she should be "married" because it's what the "creator" said, the court heard during trial.

Judge Sweeney rejected the father's explanation that he had simply told his daughter not to use the contraceptive pill and that he did so because he thought it would increase her risk of developing breast cancer.

"Overall, he was not a credible witness," Judge Sweeney said.

"Some of his evidence was so contradictory, it was difficult to believe."

She found that the father consented to the marriage and did so knowing the pair would have a sexual relationship once they were married.

"Having left them to enjoy their wedding night and having advised his daughter not to use contraception, and then making preparations for them to sleep together at his home … the inevitable conclusion is that the accused must have contemplated that they would have sex," Judge Sweeney said.

"His denial is difficult to believe in the circumstances and I do not believe it."

The father showed little emotion as he was convicted, sitting back in the dock with his arms stretched out.

He remained on bail but will return to court for sentencing next month. He faces a possible jail term.