(Reuters) - A former Israeli spymaster has branded the country´s leaders as "messianic" and unfit to tackle the Iranian nuclear program, in the strongest criticism from a security veteran of threats to launch a pre-emptive war.

Other retired officials have also criticized Prime Minister Benjamin Netanyahu and his defence minister, but the censure from Yuval Diskin, who stepped down as head of the Shin Bet domestic intelligence service last year, was especially harsh.

He was also unusual in using the language of religious fervor that Israelis associate with their Islamist foes.

"I have no faith in the prime minister, nor in the defence minister," Diskin said in the remarks broadcast by Israeli media on Saturday. "I really don´t have faith in a leadership that makes decisions out of messianic feelings."

Government officials rebuked Diskin and questioned his motives, implying that he had his eye on a political career or was settling scores after Netanyahu denied him a promotion.

The catastrophic terms with which Netanyahu and Defence Minister Ehud Barak describe the prospect of a nuclear-armed Iran have stirred concern in Israel and abroad of a possible strike against its uranium enrichment program.

Iran says the project is entirely peaceful and has promised wide- ranging reprisals for any attack.

World powers, sharing Israeli suspicions that Iran has a covert bomb- making plan, are trying to curb it through sanctions and negotiations. Those talks resume in Baghdad on May 23, but Barak on Thursday rated their chance of succeeding as low.

Although Israel has long threatened a pre-emptive strike if diplomacy fails, some experts believe that could be a bluff to keep up pressure on the Iranians, making it harder to interpret the swirl of comments from the security establishment.

FALSE IMPRESSION

Commenting on Diskin´s remarks, Amos Harel of the liberal Haaretz newspaper said the temperature was rising in anticipation of the nuclear talks.

"Nothing has been determined in the Iranian story, and the spring is about to boil over into another summer of tension," said Harel.

Diskin spoke days after Israel´s top military commander, Lieutenant- General Benny Gantz, told Haaretz he viewed Iran as "very rational" and unlikely to build a bomb, comments that apparently undermined the case for a strike.

The former Shin Bet chief was specifically damning of Netanyahu and Barak, who have often crafted strategy alone and whose rapport dates back four decades to when they served together in a top-secret commando unit.

"They´re creating a false impression about the Iranian issue," Diskin told a private gathering on Friday, where the comments were recorded. "They´re appealing to the stupid public, if you´ll pardon me for the phrasing, and telling them that if Israel acts, there won´t be an (Iranian) nuclear bomb."

Diskin said he was not necessarily opposed to an attack on Iran, though he cited experts who argue this risked backfiring by accelerating its nuclear program.

Netanyahu´s former Mossad foreign intelligence director, Meir Dagan, last year also ridiculed the Israeli war option.

Diskin went a step further by saying that Netanyahu and Barak were not up to the job of opening an unprecedented front with Iran and, potentially, with its allies on Israel´s borders.

Netanyahu is a second-term premier with solid public approval ratings and a broad conservative coalition. Barak, a former prime minister, is Israel´s most decorated soldier. But they are both technically subject to security vetting by the Shin Bet, which added punch to their panning at Diskin´s hands.

"I have seen them up close," he said. "They are not messiahs, the two of them, and they are not people who I personally, at least, trust to be able to lead Israel into an event on such a scale, and to extricate it."

Foreign Minister Avigdor Lieberman dismissed Diskin´s alarm as irresponsible "speculation," telling Israel´s Channel Two TV that such big decisions would be made at cabinet level rather than by the prime minister and defence minister exclusively.

Lieberman said Diskin, who was considered as a potential Dagan successor but was passed over, might be angry. One Barak confidant sarcastically wished Diskin "welcome to political life," implying he was angling for a slot in an opposition party ahead of an Israeli national election scheduled for next year. (Editing by Matthew Tostevin) (© Thomson Reuters 2012. 04/28/12)