They have called for a ban on the chemical Carbofuran, which is used as a cheap pesticide by local potato farmers.
Tribal poachers are laying traps for tigers by leaving recently killed animal carcasses filled with the chemical on their territories.
The tigers are believed to die within an hour of eating the carcass and the poachers then sell their lucrative skins, teeth, nails and organs for thousands of pounds to Tibetan and Chinese traders.
Conservationists called on the Indian government to follow the United States, Canada, and Kenya, where it has been banned to protect wildlife.
Officials uncovered the scale of the chemical's use by poachers when they recently interrogated a number of tribals to establish why so many tigers and leopards were being found dead without any obvious cause.
The chemical is transparent and odourless and difficult to detect in tests.
It costs under a pound for enough to kill a tiger but a single grain is enough to kill a bird.
Dr Abhishek Singh of the Endangered Flora and Fauna on Earth Conservation Team said his staff had been tipped off about the use of pesticide while investigating tiger deaths in the Kumaon Hills, the jungle landscape where the legendary tiger hunter Jim Corbett turned pioneered big cat conservation.
"The poachers used to use steel traps to catch tigers but there was always risk of getting caught. Pesticides are easy to use and pose no danger to the poachers. They apply the pesticide to the carcass of dead animals used as a bait for the tiger and wait for him to consume it. One kilogram of the pesticide is enough for a carcass and single bite can led to the tigers death within an hour," he said.
"There has been increased demand for tiger bones and teeth in Tibet. Nails, teeth and bones of a tiger can fetch 15 lakh rupees (£16,500) in the Tibetan market," he added.
India's tiger population has declined by 90 per cent in the last century to just 1,706 today, though there have been signs of a small increase in numbers in the last two years.