Israel's parliament, the Knesset, has held an extraordinary session to debate a damning report on the handling of last year's conflict in Lebanon.
Shimon Peres (r) spoke to defend the prime minister
Opposition leader Benjamin Netanyahu called for PM Ehud Olmert to resign, but Kadima MPs backed Mr Olmert and a vote of no-confidence was not held.
The study was highly critical of the prime minister, and Foreign Minister Tzipi Livni has called on him to quit.
Thousands of Israelis are preparing to gather in Tel Aviv for a protest rally.
Recent opinion polls have suggested that a majority of Israelis want Mr Olmert to stand down.
After a six-month investigation led by retired judge Eliahu Winograd, Mr Olmert was accused of "serious failure in exercising judgement, responsibility and prudence".
But Mr Olmert is refusing to quit, saying he will implement the report's recommendations.
Mr Netanyahu, head of the right-wing Likud party, told the Knesset that Israel's inability to win a clear victory against the Hezbollah militia meant those in power should be replaced.
"Those who failed at war cannot be those who correct the failures," he said.
Mr Olmert attended the debate but did not speak, his deputy Shimon Peres instead defending the prime minister.
"He who doesn't try, doesn't fail," he said.
"This government was instructed by the inquiry to immediately fix what needs fixing and it is doing so."
The BBC's Tim Franks, in Jerusalem, says the report does not just detail institutional failings, but the prime minister's own personal flaws, politically and intellectually.
For the time being the prime minister is fighting back, our correspondent says, but it is hard to see Mr Olmert surviving in the long term, our correspondent adds.
On Wednesday the foreign minister, Ms Livni, added her voice to the calls for Mr Olmert to resign telling reporters that she had told the prime minister that quitting "would be the right thing for him to do".
She said she would not resign from the government or try to oust Mr Olmert herself, but would stand as a candidate to replace him.
"It's not a personal matter between me and the prime minister - this issue is more important than both of us," she said.
"However, large-scale change is needed now."
Ms Livni, who was a founder member of Kadima when it was formed by former Prime Minister Ariel Sharon, also serves as deputy prime minister.
Defence Minister Amir Peretz and the former military Chief of Staff Dan Halutz were also heavily criticised by the report into the conduct of the 34-day conflict with Hezbollah.
The inquiry, commissioned by Mr Olmert, did not explicitly call for resignations.