Iran on Tuesday mocked Israeli officials for flirting with "stupid ideas" after former Israeli spy chief Meir Dagan admitted that an Israeli attack on Tehran's nuclear sites was foolish.

"It is interesting that Zionist regime officials admit they have stupid ideas, as they have had so many such ideas in the past," foreign ministry spokesman Ramin Mehmanparast said at his weekly press conference.

His remarks came after former Mossad head Dagan said on May 6 that the possibility of a future Israeli aerial attack on Iran "would be stupid."

Dagan, who retired in January after eight years as director of the Israeli intelligence service, suggested that the attack could fail to curb Iran's atomic ambitions while risking engulfing the region in conflict.

"Anyone attacking Iran needs to understand that it could start a regional war, which will include missile fire from Iran and Hezbollah in Lebanon," he said.

"The Iranian problem must be made an international problem and we must continue to work to delay the nuclear programme."

His remarks, the first he has made publicly since retiring, put him at odds with Israel's government, which says it reserves the right to attack Iran's nuclear programme if international efforts to halt it fail.

Iran maintains that its nuclear work is purely for peaceful purposes, but Western nations fear that Tehran is clandestinely building nuclear weapons.

Israel considers the prospect of a nuclear-armed Iran as a threat to its existence.

Meanwhile, Israeli Defence Minister Ehud Barak declared last week that even if Iran manages to acquire atomic weapons it would not use them against the Jewish state.

Iran will not drop a nuclear bomb on Israel, "not on us, not on any other neighbour," Barak told Haaretz newspaper. "I don't think in terms of panic," he added.

Mehmanparast brushed aside the comments.

"Remarks of the illegitimate regime's officials bear no importance for us... We have stated on numerous occasions that our nuclear activities are peaceful and are being conducted under the supervision of the (International Atomic Energy) Agency," he said.