An anti-1080 group is threatening to bring down Department of Conservation helicopters if it drops the controversial pesticide in Taranaki's Egmont National Park.
The threat comes just a month after the group, called the New Zealand Hunters, illegally released dozens of sika deer into north Taranaki forests in what DOC believes is retaliation for dropping 1080.
In a letter sent to DOC and media organisations on Tuesday, the group has threatened to mount a war against the use of the pesticide.
"This will be a war like no other, you watch this happen around you," it reads.
"We the hunters of New Zealand have had enough of your bloody lies.
"We will take down helicopters who support 1080 drops.
"We will take down people one by one, blood will fall. Watch this happen."
The letter says the group intend to pick up pellets and target open milk vats and the inside of meat processing companies.
"Be warned DOC, these hunters have more guns than you or the police.
"There is no respect for you bastards any more. Let the war begin.
"Just be very careful, stop using 1080."
DOC and the police confirmed to Fairfax that they were investigating the threats. In October, Game Animal Council chairman Don Hammond said releasing the deer was a mindless act.
"While there have been issues surrounding the use of 1080 in our environment this is not the way to deal with them," he said.