Israel 'prepared for 30-day war with Iran'
Israel was prepared, he said, though strikes on Iran's nuclear facilities had to be co-ordinated with the US.
Meanwhile, a US blogger has published what he says are Israel's attack plans.
Richard Silverstein told the BBC he had been given an internal briefing memo for Israel's eight-member security cabinet, which outlined what the Israeli military would do to prevent Iran developing nuclear weapons.
AnalysisThe text of the purported Israeli cabinet memo is just that, text. There is no document as such and thus it is impossible to verify if it is indeed an Israeli cabinet paper of some kind. But its purpose for Richard Silverstein is clear. He believes it was passed by a serving officer to the politician and then leaked by him precisely to alert the outside world to the scale of Israel's military plan to strike at Iran and thus to reduce the chances of it ever happening.
An unprecedented public debate is under way in Israel on the wisdom of launching an attack against Iran. And this leaked document, whatever its source, and whatever its original purpose, has become an element in that debate.
The document itself is striking in both the scale and scope of the military operation that it proposes. It also employs a range of technologies, many of which we have known that the Israelis are developing, but this document suggests that they are battle-ready and fully operational.
The purported leaked Israeli memo suggests that the military operation would begin with a massive cyber-attack against Iran's infrastructure, followed by a barrage of ballistic missiles launched at its nuclear facilities.
Military command-and-control systems, research and development facilities, and the homes of senior figures in nuclear and missile development would also be targeted.
Only then would manned aircraft be sent in to attack "a short-list of those targets which require further assault".
BBC diplomatic correspondent Jonathan Marcus says it is not possible to verify the authenticity of the document, but the proposed mission would be huge and have potentially far-reaching consequences.
Iran's government and military have made it clear that if it is attacked either by Israel or the US, it will respond in kind, either directly or through proxies.
In his interview with Maariv, Mr Vilnai said Israel had "prepared as never before".
"There is no room for hysteria," said the former general, who is stepping down at the end of August to become Israel's ambassador to China.
"There might be fewer dead, or more, perhaps... but this is the scenario for which we are preparing, in accordance with the best expert advice."
"The assessments are for a war that will last 30 days on several fronts," he added, alluding to the possibility of attacks by the Iranian-backed Lebanese Shia Islamist movement, Hezbollah, and Palestinian Islamist militants in the Gaza Strip.
Mr Vilnai also declined to comment on US Defence Secretary Leon Panetta's assertion on Tuesday that Washington did not believe Israel had yet made a decision on whether or not to launch a strike on Iran.
"I don't want to be dragged into the debate," he added. "But the United States is our greatest friend and we will always have to co-ordinate such moves with it."
On Tuesday, Israeli Prime Minister Benjamin Netanyahu announced that Mr Vilnai would be succeeded by Avi Dichter, a former head of Israel's internal security agency, Shin Bet.