In unusually candid comments set to ratchet up tensions over Iran at the top of Israel's political establishment, Yuval Diskin, who retired as head of the internal intelligence agency Shin Bet last year, said he had "no faith" in the abilities of the prime minister, Binyamin Netanyahu, and the defence minister, Ehud Barak, to conduct a war.
The pair, who are the foremost advocates of military action against Iran's nuclear programme, were "not fit to hold the steering wheel of power", Diskin told a meeting on Friday night.
"My major problem is that I have no faith in the current leadership, which must lead us in an event on the scale of war with Iran or a regional war," he said.
"I don't believe in either the prime minister or the defence minister. I don't believe in a leadership that makes decisions based on messianic feelings. Believe me, I have observed them from up close ... They are not people who I, on a personal level, trust to lead Israel to an event on that scale and carry it off.
"They are misleading the public on the Iran issue. They tell the public that if Israel acts, Iran won't have a nuclear bomb. This is misleading. Actually, many experts say that an Israeli attack would accelerate the Iranian nuclear race."
Government aides described Diskin's comments as irresponsible and motivated from personal frustration.
Diskin's remarks followed a furore over comments made on Wednesday by Israel's serving military chief, Benny Gantz, which starkly contrasted with Netanyahu's rhetoric on Iran. Gantz said he did not believe the Iranian leadership was prepared to "go the extra mile" to acquire nuclear weapons because it was "composed of very rational people" who understood the consequences.
In what was seen as a veiled rebuke to the prime minister, Gantz added: "Decisions can and must be made carefully, out of historic responsibility but without hysteria."
The chief of staff later attempted to gloss over suggestions of a breach between the military and political leaderships, telling reporters there was "really no distance" between his view and the prime minister's.
Neither Netanyahu nor Barak have moderated their rhetoric. The prime minister recently said that those who downplayed the threat from a nuclear Iran "have learned nothing from the Holocaust". He added: "The Iranian regime is openly calling for our destruction and working frantically for the development of nuclear weapons as a means to that end."
On Thursday, Barak said the chances of Iran halting its nuclear programme in response to international sanctions appeared low. Iran, he said, was not "rational in the western sense of the word".
Diskin's comments also put him in agreement with the former head of the Mossad, Meir Dagan, who has said that attacking Iran was "the stupidest thing I have ever heard" and that the Iranian regime was rational.