The world health body also asserted that the implementation of 85 per cent warning display will uphold India's position as a global leader in health and save precious lives.
The comments come days after a Committee on Subordinate Legislations recommended the reduction of the principal display area to 50 per cent, inviting flak from MPs, health experts and cigarette companies.
"The current debate on reducing size of pack warnings, especially on bidis and smokeless tobacco is worrisome, especially because large and prominent health warnings have shown to be a cost-effective means of increasing public awareness of the health effects of tobacco use and in reducing tobacco consumption," Henk Bekedam, WHO Representative to India said.
He said in India, nearly a million deaths occur annually due to tobacco.
Health Ministry's deadline for implementing the 85 per cent warning size norm is April 1.
"Today, as India stands on the threshold of hosting the seventh session of the Conference of the Parties (COP7) in November 2016, implementation of the 85 per cent pictorial health warnings on both sides of all tobacco packs and the development of a comprehensive tax policy for tobacco products will uphold India's position as a global leader in health and save precious lives," he said.
Bekedam said any reduction in size of pack warnings will be a great setback for public health in the region, as neighboring countries, including Nepal (90 percent), Thailand (85 percent), Pakistan (85 percent), Sri Lanka (80 percent) and most recently Myanmar (75 percent) have overcome similar challenges and notified large pictorial warnings.