JERUSALEM (Reuters) - Israeli Prime Minister Ehud Olmert's future appeared increasingly in doubt on Wednesday after a senior member of his party urged him to resign in the wake of criticism of his conduct of last year's Lebanon war.
Avigdor Yitzhaki, one of the most influential lawmakers in Israel's parliament, said Olmert had lost the confidence of his centrist Kadima party and the nation.
Deputy Prime Minister and Foreign Minister Tzipi Livni planned to meet with Olmert later in the day to deliver what Israeli media reports described as "an ultimatum".
The reports said Livni would tell Olmert to resign quickly or she would lead a revolt against him within Kadima.
Livni, a frontrunner to replace Olmert if he resigns, was earlier quoted telling aides "he must go" following the release of a report by a government-appointed commission blaming Olmert for serious failures during the Lebanon war.
Defence Minister Amir Peretz is considering stepping down as early as Wednesday over the criticism leveled at him, Israel Radio and Army Radio reported.
Convening his first cabinet meeting since the report was released on Monday, Olmert acknowledged failings and a majority of his cabinet said ministers were collectively responsible.
"Clearly the report points to very serious failings by the whole government, and naturally my failings as its head," Olmert said. "It is primarily incumbent on this government, which is responsible for the failings, to also be responsible for fixing them.
"I suggest that all those who are in a hurry to take advantage of this report and make political gain -- slow down."
Olmert won approval from his cabinet to appoint a committee to oversee the implementation of the changes recommended by the Lebanon war commission.
A majority of cabinet ministers said during the meeting they were "collectively responsible" for the failings during the war, cabinet secretary Yisrael Maimon told a news briefing.
He said he hoped members of the cabinet would not resign since that would only undermine efforts to implement the commission's recommendations.
Olmert "made up his mind hastily" to launch the campaign last July against Hezbollah guerrillas, the government-appointed panel said in an interim report, accusing him of "a serious failure in exercising judgment, responsibility and prudence".
His declared aims in going to war, to free two soldiers seized by Hezbollah and crush the militant group, were "overly ambitious and impossible to achieve", the Winograd commission said of the 34-day conflict.
Former army chief Dan Halutz stepped down earlier this year and the fallout from the commission report began on Tuesday with the resignation of a cabinet minister from Olmert's main governing partner, the Labour Party.
The political storm quickly spread to Kadima, whose members in parliament have started drafting a letter urging Olmert to quit over the report's findings.
"A leader can only lead a public where he has, firstly, legitimacy and its confidence. The prime minister should act responsibly and resign to allow a new coalition to be formed by Kadima," Yitzhaki, Kadima's faction leader, told Israel Radio.
"I will tell the parliamentary party today that the prime minister must resign and if he does not do so, I will quit as leader of the coalition."
The two frontrunners to replace Olmert are Livni, a former Mossad intelligence operative, and Deputy Prime Minister Shimon Peres who has been prime minister on two previous occasions.
Former prime minister Benjamin Netanyahu of the rightist Likud party, a favorite in opinion polls, could also pose a challenge if Olmert's government is toppled.