The Fijian national, who has New Zealand residency, pleaded guilty to 26 charges of encouraging a person to breach their visa conditions and exploiting an unlawful employee by failing to provide holiday pay and minimum wage.
"Most workers who were hooked into this scam were, as you will hear, poor people living in difficult circumstances often on low wages and often with no experience of travelling overseas," Crown prosecutor Luke Clancy told the jury in his opening address.
"It's exploitation pure and simple," he said.
People trafficking is about arranging the entry of migrants into New Zealand by deception, Clancy told the court, adding that Ali had "deliberately and repeatedly flouted the law".
Some of the migrant workers lived in Ali's property in Auckland and worked for his gib fixing business, while others were sent down to work on kiwifruit orchards in the Bay of Plenty, the court heard.
The workers were allegedly forced to work six days a week unless it was raining, paid below minimum wage, denied holiday pay and forced to cover the costs for their own accommodation, bedding, food and transport to and from work, Clancy told the court today.
Clancy claimed Ali was the "driving force behind the scam", which included the help of his wife and sister-in-law who ran a travel agency offering the New Zealand employment from Suva, Fiji.
Many of the workers came from "difficult or deprived conditions" and had borrowed heavily from their families and friends to afford the steep fees Ali and his associates charged to arrange the visas and accommodation, Clancy told the court.
"Instead of having the opportunity to work and make money they were exploited, left with nothing and had to return home to Fiji ashamed and having to explain to the people they had borrowed money from that they had been ripped off," Clancy said.
Defence lawyer Peter Broad told the jury the alleged misrepresentation of the migrant workers occurred in Fiji, while Ali was in New Zealand.
"Please keep in mind what Mr Ali knew," Broad urged.
During a Sunday church service, one of the workers, Suliana Vetanivula, confided in a fellow churchgoer who blew the whistle to Immigration New Zealand, the court heard.
The alleged offending occurred between May 2013 and March 2015.
All 15 Fijian workers are expected to take the stand during the six-week trial.