Police were alerted to a couple pimping out a 15-year-old after the girl's mum discovered on social media she'd been flown from Christchurch to work in central Auckland brothels.

Taton Sebastian Smith, 35, and Tahleicia Elizabeth Seil, 25, were sentenced last Friday in the Auckland District Court by Judge Eddie Paul for assisting someone under 18 to provide sexual services.

Smith was jailed for two years and 10 months, while Seil will serve nine months' home detention after they had earlier pleaded guilty.

Both also were also sentenced for profiting from the activity, and Smith for having sex with a person aged 12 to 16.

The couple, who were in a relationship, were operating an internet escort agency from at least the start of 2014 from several central Auckland properties, court documents released to the Herald show.

At the beginning of June 2016, Smith and Seil identified a 15-year-old girl living in Christchurch as someone to work for them.

A sex worker employed by Smith and Seil first established the contact between the teen and the pair.

Smith and Seil then arranged and paid for the teen to fly from Christchurch to Auckland and begin working in their central city brothels.

The girl told the couple she was 16 or 17.

After collecting her from Auckland Airport, Smith drove her to a city apartment close to one of the brothels.

He told the teen she would be "good at sex and perfect for sex work", court documents show.

The couple were driven by greed and the earnings they were going to make, the judge said. Photo / Dean Purcell

Smith would later also have sex with the 15-year-old, who was then advertised online.

Over the next four days the pair managed bookings for the teen via text and calls they received from their clients, with Smith and Seil planning to take a third of the profits.

But on June 4, 2016, the teen's mum discovered social media messages between her daughter and Smith and Seil and alerted police.

"Fortunately police were notified by the person's mother and they acted immediately," Judge Paul said during Smith and Seil's sentencing.

The teen was rescued from one of the brothels by police, who also arrested the couple.

Smith admitted to officers he had arranged the sexual services for the teen but said he didn't know how old she was.

Seil also said she assumed the teen was at least 18.

However, Judge Paul was not convinced.

"Both these defendants were well aware this girl was under 18 years old," he said.

He added the pair were "driven by greed" and the earnings they were going to make.

Judge Paul accepted the Crown's argument Smith and Seil had "clearly planned and organised" to sexually exploit the vulnerable teen.

Detective Senior Sergeant Geoff Baber, of Auckland City Police's Child Abuse and Sexual Crimes Unit, told the Herald sadly there were underage sex workers in New Zealand.

"There are reports that have been made to, and investigated by, police," he said.

"While we are unable to go into specific details around the methodology used in these types of investigations, police take any case involving the sexual exploitation of minors extremely seriously and we have a dedicated team of trained specialist staff who work in this sensitive area."

He said anyone who is aware of a similar case to the teen's or if someone knew of illegal activity involving underage sex workers, they should contact police.

"Our priority is ensuring the safety and wellbeing of the child or young person involved," Baber said.

Earlier this year, the Herald revealed one of New Zealand's most sickening criminal cases and just the third conviction for slave trading in the country's legal history.

Kasmeer Lata was jailed for six years and 11 months in April for keeping her daughter as a sex slave, turning her Auckland home into a brothel, and selling the 15-year-old to men some 1000 times over a two-year period.

Justice Matthew Muir said at Lata's sentencing: "New Zealand's courts will not [tolerate] the prostitution of children."

Her partner, Avneensh Sehgal, who attempted to flee to India, was also imprisoned.

And just last month, the Herald reported on a Lower Hutt woman who planned to sexually exploit her 10-year-old granddaughter to sex criminal Andrew Davie.

Davie was jailed for three years and five months, while the grandma was sentenced to three years and three months in prison.