West Coast Police are investigating a group of anti-1080 activists who sent a threatening letter to several organisations about upcoming poison drops.
They said the letter suggested that any person directly or indirectly involved with the 1080 drop was committing an act of terrorism.
West Coast Area Commander Inspector Mel Aitken said the suggestion was completely false.
She said while the group was entitled to peaceful protest - any threat made against others would be taken seriously.
In December last year, a hand written letter believed to be from anti-1080 campaigners and sent to the department's New Plymouth office, threatened to shoot Department of Conservation helicopters out of the sky.
The chair of 100 Percent Pure Taranaki, Chris Wilkes, believed the December letter was written to undermine environmentalist groups.