Former Northland cop Mark Franklin has been sentenced to a year in prison in the Cook Islands for selling drugs.

Franklin, who used to be a New Zealand detective inspector, was sentenced this morning in the Cook Islands High Court by Justice Colin Doherty, after pleading guilty last week to two counts of selling cannabis, and one count of offering to sell cannabis.

He was arrested in Rarotonga in 2011, over allegations that he was operating as a local drug dealer, selling cannabis from a bar.

Franklin, who has been living as a musician in Rarotonga, was represented by New Zealand-based barrister Paul Dale with help from Cook Islands lawyer Tony Manarangi.

Mr Dale said they have not yet decided whether they will appeal the sentence, which he described as ``harsh''.

He did not want to comment further. ``The right of appeal is being weighed up and I wouldn't want to pre-empt that.''

Franklin was caught in a drugs investigation, Operation Eagle, which netted 13 people including a Cook Islands policewoman, an expat bar owner and the former deputy prime minister's son.

Two of Franklin's co-accused - Riki Carlson and Mere King - were also sent to prison this morning. Four other defendants were sentenced to prison in separate trials over the past year.

There is a significant difference in the way Class C drugs are treated in the Cook Islands, which has a much harsher maximum sentence for possession of cannabis than New Zealand.

The maximum sentence in New Zealand for cultivation is seven years, while in the Cook Islands it is 20 years.

While the maximum sentence in New Zealand for possession is three months, in the Cook Islands it is two years.

Franklin was the Northland crime services manager during his tenure in the region.

At that time he was in charge of all serious criminal investigations, drug enforcement teams, asset seizures, specialist squads and crime strategy.

- APNZ