Rafsanjani was referring to Thursday comments by the International Atomic Energy Agency's chief for inspections, Olli Heinonen, about intelligence suggesting Iran was engaged in weaponisation studies in the past.
"Yesterday Mr. Heinonen said they had gathered information from 10 countries and that Iran should provide answers. It is clear that they have spread a new trap for us," the cleric said in a Friday sermon carried live on state radio.
World powers "are not after such information but they intend to obtain a pretext to serve the bad aims over which they have confronted our nation over its lawful rights," Rafsanjani said.
In its latest report, the IAEA expressed "serious concern" that Iran was still hiding information about alleged studies into making nuclear warheads and defying UN demands to suspend uranium enrichment.
Tehran has repeatedly dismissed the intelligence as "fabricated," and the allegations that it was seeking to build a bomb as "baseless".
"I believe if the IAEA goes on like this it will lose its credibility among members," said the influential cleric, who heads Iran's top arbitration body, the Expediency Council.
Western countries such as the United States, which is spearheading international efforts to thwart Iran's nuclear drive, insist that Tehran should actively disprove the allegations rather than simply dismiss them as untrue.
Iran is already under three sets of UN Security Council sanctions over its refusal to suspend uranium enrichment work, which can be used to make the fissile core of an atom bomb as well as nuclear fuel.
The West fears Iran could use its nuclear programme to make atomic weapons.
Iran insisting its nuclear programme is aimed at peaceful ends and energy production and says it is ready to negotiate with world powers to alleviate concerns over its nuclear ambitions.
However, the Islamic republic has so far rejected halting uranium enrichment as a pre-condition to talks, insisting it has a right to the activity as a signatory to the nuclear Non-proliferation Treaty.
Rafsanjani called on the IAEA and world powers to negotiate with the Islamic republic, warning that "threats and pre-conditions will drive them away from their aims and force Iran not to be able to cooperate."
The IAEA's Monday report prompted a warning from Iran's new parliament speaker Ali Larijani, who said on Wednesday the country could review its relations with the UN watchdog.
Larijani, who used to be Iran's chief nuclear negotiator, did not say how Iran could alter its cooperation, but any move from Tehran to limit IAEA talks or inspections would raise tensions in the standoff.
