"We should remain firm and not put our existence in danger by signing the additional protocol," said Hossein Shariatmadari, editor of the hardline Kayhan newspaper, in comments carried in the national press.
The International Atomic Energy Agency (IAEA) has given Iran until October 31 to answer all its questions concerning allegations that it is seeking to develop atomic weapons.
The international community is also calling on Iran to sign an additional protocol to the Nuclear Non-Proliferation Treaty which would allow inspectors to conduct surprise visits to suspect sites. IAEA teams are currently only permitted to make pre-arranged visits.
But Shatmadari said the additional protocol was merely the "first step in a plan slowly to overthrow the Islamic republic."
The editor, well-known for his radical hardline views, is one of several conservatives urging Iran to follow the path of North Korea and pull out of the NPT altogether.