The person who threatened to contaminate infant formula with 1080 poison doesn't exist, says Westport anti-1080 activist Pete Lusk.
He believed the threat had been manufactured, and the subsequent investigation of anti-1080 activists was a smear campaign designed to discredit the anti-1080 movement.
In November last year, Fonterra and Federated Farmers received anonymous letters and milk packages contaminated with 1080.
The letters said New Zealand milk products, namely infant formula, would be contaminated with 1080 if the Government did not stop using the poison for pest control.
The public was made aware of the threat in March, nearly four months later.
Mr Lusk said the situation was a charade turned PR stunt.
"It's becoming clear to a lot of us in the anti-1080 movement that the 'blackmailer' does not exist.
"We were wary from the start when the 1080 in the blackmailer's letter was shown to be in pure form and such crystals are only available to someone well up the supply chain."
Many anti-1080 activists' suspicions were first raised when the detectives who visited them didn't seem to have their heart in the investigation, he said.
"It's just like they knew something was amiss way up the food chain."
Some of the people being investigated were also old and hadn't said anything against 1080 for years, he said.
One was a retired doctor from Otago who was over 80.Most people in the anti-1080 campaign were just average citizens, Mr Lusk said.
"On the West Coast, we know of two women who are vocal campaigners who have not been questioned at all, yet their husbands have."
In Golden Bay a quiet old couple had 10 police arrive at their place and were hauled off to separate police stations for hours of questioning.
"The investigation into the contamination threat, named Operation Concord, was all about placing psychological pressure on anti-1080 activists, he said.
"The aim of the Government is to set up distrust and hopefully blow our movement apart."
A police spokesperson said Operation Concord was a significant ongoing investigation into a serious threat of blackmail.
The investigation team continued to make steady progress, with over 120 people approached and interviewed, the spokesperson said.
"The investigation team remains very focused on finding the person or persons responsible, and we are unable to speculate on how long the enquiry may take."
Police were keeping an "open mind" on who may be responsible, and were talking to a range of people who may have information which could assist the investigation.
"To date the majority of people we have spoken to have been willing to assist us, and we remain grateful for their co-operation."
Police would not discuss any specific individuals or areas of the country which the enquiry team had focused on, the spokesperson said.
According to One News, the Ministry for Primary Industries (MPI) estimated the threat had cost the country close to $800,000.
However, that figure didn't account for the significant amount of time Government staff had spent dealing with the issue, the ministry said