The Auckland businessman who threatened to spike infant milk formula with 1080 poison has had 15 months added to his sentence after he was caught in a party pills sting with buckets of illegal drugs.

Photo: RNZ / Todd Niall

Jeremy Hamish Kerr was back at the High Court in Auckland today where he was sentenced for earlier charges of possessing and selling illegal party pills.

He is serving a prison sentence of eight and-a-half years for blackmail after sending anonymous letters to dairy giant Fonterra and Federated Farmers in November 2014, in the hope the government would ban 1080.

He later admitted five separate charges - one of selling the illegal pills and four of possession for supply.

Justice Venning told the court today Kerr's motivation was money. He said Kerr was a businessman, took a business risk in dealing drugs and got caught.

His lawyer, John Billington QC, said the saga brought to an end a sad period of Kerr's life and he was confident he would not appear before the courts again.

Kerr had been caught in a police surveillance operation in 2011.

Officers watched as Kerr met with their target at a cafe in South Auckland. They then followed him to a public storage unit in East Tamaki.

They later carried out secret searches of the storage unit where they found a variety of pills, powders and pill pressing equipment.

They found buckets of powder, containing BZP and TFMPP - which when combined has similar effects to MDMA or ecstasy.

Another search two months later found thousands of pills in zip lock bags marked with "x" "CK" and pink doves.

According to police, the pills had a wholesale value of between $20 and $40, meaning the 32,000 pills would have a value of between $640,000 and $1.2 million.

Kerr later told police he was only getting $2 a pill, because he'd had the BZP since before 2005 when it was outlawed and it would now be "low strength".

In the Auckland District Court in 2012, Judge Cunningham granted Kerr name suppression, and said because of his reputation as a reputable businessman, he was unlikely to reoffend.

However, he did just that.

While these charges were before the court, Kerr sent the blackmail letters to Fonterra and Federated Farmers.

At sentencing for the blackmail charges in March this year, Justice Venning noted that Kerr manufactured an alternative to 1080 poison and financial gain was the motivation behind the blackmail.

In sentencing today Justice Venning noted Kerr had a previous conviction for growing and selling cannabis. He took time off for the guilty plea and took into account Kerr's 8 and-a-half year sentence for blackmail.

The cost of the 1080 investigation to agencies was about $37m and Justice Venning said it could have had a catastrophic effect on the New Zealand export industry.