A man previously jailed for 12 and a half years for dealing meth, cannabis and BZP has had an extra 10 months added to his jail term for methamphetamine offending.

Photo: RNZ

The jailing of Clint Helmbright and his co-accused, Lewis Padden, brings to an end Operation Nebraska - a police investigation which began in 2013.

Padden was jailed for seven years, having been found guilty at trial of supplying a total of 168 grams of methamphetamine to Helmbright.

However, Justice Thomas said Helmbright also had other methamphetamine supplies, dealing between 250 and 300 grams of the drug.

Following an earlier trial, Helmbright had been found guilty of 38 charges, including 19 related to dealing methamphetamine.

Crown lawyer Emma Light told the High Court in Wellington today both men were involved in an ongoing commercial drug enterprise.

"There was no evidence Padden was a heavy user selling to support his own habit and likewise with Helmbright."

"While it's accepted he was using, his network clearly went beyond supporting his own habit which does aggravate matters; that it was a commercial deal for profit."

Helmbright's lawyer, Eric Forster, said the court must recognise the lengthy jail term already imposed and the fact his client was making "a good fist" of his time in prison.

"Helmbright hasn't offended since the 1980's and is capable of reform."

"Maybe there's a diminishing return in having him in custody longer at the taxpayer's expense."

However, Justice Thomas said there was no dispute the men were involved in a commercial drug operation and their offending was premeditated.

"[Their offending was] based on Mr Padden supplying relatively large amounts of methamphetamine to Mr Helmbright, who broke it down into smaller amounts."

"The evidence disclosed clandestine meetings ... Mr Padden was particularly cautious and alert to being surveyed.

"They used code [words] to discuss [their drug deals] and Mr Helmbright also used codes with his drug runners."

Padden's lawyer, Brian Yeoman said his client's offending was a significant fall from grace for a man who had previously run successful businesses.

"He has been a panel beater most of the time and the variety of things he has done ... the business enterprises, show a man of considerable talent and it's sad to be now before the court for sentencing in relation to this offending."

Justice Thomas declined to impose minimum terms of imprisonment on the men, as requested by the Crown.