The draft to be put before the board of governors of the International Atomic Energy Agency (IAEA) by Britain, France and Germany next week "gives the impression that Europe and the United States are working together to deprive Iran of nuclear technology," Rafsanjani told worshippers at the main weekly Muslim prayers in Tehran.
"If that is the case, they will regret it," warned the former president who remains extremely influential within the Islamic regime.
The board of governors is expected to begin its meetings in Vienna on Monday.
The draft "reflects the position of the United States and some Western countries," Rowhani, who is in charge of Iran's nuclear affairs, told state television.
Rafsanjani reiterated that Iran "will make no concession" on its right to possess civilian nuclear technology while recalling Tehran's objection to military nuclear power and its determination to cooperate with the IAEA.
If the IAEA fails to change the European draft, Rohani warned, "we will conclude that the European Union does not live up to its commitments and that will affect the decisions of the Islamic Republic's leaders."
The draft presented by Britain, France and Germany on Tuesday to the IAEA board of governors stops short of provoking a showdown over Tehran's alleged secret weapons programme, diplomats said.
However, it sharply criticizes Iran for failing to answer questions about alleged nuclear weapons activities, diplomats told AFP.
Conservatives and reformers alike hit out at the draft.
The draft urges Tehran to clarify urgently the origin of contamination by highly enriched uranium and calls for full disclosure on a program of centrifuges used to enrich uranium.
They are asking Iran to suspend immediately and fully all enrichment-related activities.
Tehran meanwhile is counting on the Europeans to block the US plan to send the case before the UN Security Council which would consider international sanctions.
However, with the European draft which the Americans are likely to support, many in Iran fear that the Europeans have abandoned the Islamic republic.