"If the IAEA again acts in the way that the Americans want and if the big powers use the Non-Proliferation Treaty to pressure Iran, parliament will examine leaving the NPT," MPs Ali Abaspour and Hossein Nejabat told the hardline Jomhuri Islami newspaper.
The warning comes ahead of a June 14 meeting of the Vienna-based International Atomic Energy Agency (IAEA), where the body's executive -- the Board of Governors -- are due to review the progress of inspections of Iran's suspect bid to generate nuclear power.
Abaspour said the outcome of the meeting would "serve as a basis" for a decision in parliament on how Iran should handle its future relations with the IAEA, including whether it ratifies an additional protocol to the NPT that allows tougher inspections.
"If the IAEA acts in an independent manner, parliament will insist on continued cooperation," said the MP, one of a majority of conservative deputies who seized control of the Majlis after most reformist candidates were barred form standing in February's parliamentary polls.
"But if we see that the IAEA is simply a tool of the United States and is only looking for pretexts to use against Iran, we will put on parliament's agenda a move to leave these treaties," he warned.
The United States argues Iran is secretly trying to build the bomb, but Iran insists its programme is purely peaceful -- even though it emerged late last year the country had for years been covering up sophisticated activities.
In the run-up to the June meeting, Iranian officials have been warning the IAEA not to be too harsh, or else risk pushing the Islamic republic's clerical leaders to cut off cooperation altogether.
IAEA chief Mohamed ElBaradei said last week that Iran's cooperation with the agency had been insufficient, but added that he had not drawn any conclusions over the nature of the country's nuclear programme.
If Iran comes under renewed criticism on June 14 and more doubts emerge over its cooperation, the IAEA's board could refer the matter to the UN Security Council, which in turn could decide to impose sanctions.