A father and son involved in a Bay of Plenty police operation targeting the Kawerau Mongrel mob will remain in prison.

Kawerau Mongrel Mob leader Frank Milosevic, 52, has been sentenced to 17.5 years imprisonment after being found guilty on 16 drug and money laundering related charges.

He has received a minimum non parole period of eight years and nine months.

Slobodan Milosevic, 30, was sentenced to 16 years and nine months imprisonment with a non-parole period of seven years and 10 months.

Slobodan was found guilty of 19 charges involving methamphetamine and cannabis at an eight week trial in the High Court at Hamilton last year.

Both Frank and Slobodan appeared in Tauranga District Court today via audio visual link from prison.

A third man facing four charges relating to supply, possession and selling of methamphetamine also appeared in court today.

Keith Pryor, 48, was sentenced to six years and nine months imprisonment.

The men were arrested after a six-month police operation in 2017 and 2018 called Operation Notus.

Senior Sergeant Al Fenwick, who was a sergeant in Kawerau during that time, told the Whakatane Beacon Notus was the biggest police operation in the town's history.

The Whakatane Beacon reports that more than 50 people involved in the operation are facing charges.

In court today Judge Mabey said that Frank abused his mana as president of the Mongrel Mob in Kawerau.

"There is no doubt you were head of a substantial drug operation in a community that must have been adversely affected by what you did."

Frank was a serious criminal within a community where he was greatly respected, Judge Mabey said.

Judge Mabey said 30-year-old Slobodan was the right-hand man, with the father and son pair being "effective and well-organised" in their drug activity.

"You are an intelligent, resourceful man with a strong work ethic. If you and your father had engaged in a legitimate business I am sure you would succeed."

After Slobodan received his sentence, people in the public gallery began barking and jeering.

Slobodan is the father of three children, and his partner is due to have a fourth child later this year.