Tony Blair has again insisted intelligence documents on Iraq's weapons programmes were not changed on the orders of Downing Street to strengthen the case for war.
Blair says the charges are totally untrue
Announcing that Parliament's all-party intelligence and security committee would be conducting an inquiry into the row, the prime minister said the allegations were "completely and totally untrue".
Conservative leader Iain Duncan Smith said the credibility of the government was now at stake in the row.
But a Liberal Democrat motion, backed by the Tories, calling for an independent judicial inquiry, was defeated by 301 votes to 203 on a government majority of 98.
The vote, which saw just 11 Labour MPs rebel, came at the end of a debate about the Iraq intelligence.
During the debate, former cabinet minister Clare Short said her briefings from the security services made her believe the intelligence had been exaggerated.
"The fact there was deceit on the way to military action is a very grave accusation because if we can be deceived about this what can we not be deceived about," she said.
Critics reportedly faced a showdown with John Prescott at the weekly meeting of Labour backbenchers.
"This is all about the integrity of the party - and the prime minister does not lie," Mr Prescott told them, according to London's Evening Standard newspaper.
In the Commons, Mr Blair backed a claim by cabinet minister John Reid that "rogue elements" in the intelligence services were briefing against the government.
But he said he was convinced that nobody from the Joint Intelligence Committee (JIC) - which briefs ministers on security matters - was involved.
Mr Blair said one claim being disputed - that Iraq could launch weapons of mass destruction within 45 minutes of an order being given - was entirely the work of the JIC.
Launching a vigorous defence of the government's approach to Iraq, Mr Blair said work on finding the weapons was just beginning.
A newly expanded team of about 1,400 people from the US, UK and Australia was only now stepping up the search.
"I have absolutely no doubt at all that they will find the clearest possible evidence of Iraq's weapons of mass destruction," he said.
'Credibility at risk'
Mr Blair urged MPs to remember that as well as the weapons issue "the people of Iraq are delighted that a brutal dictator that murdered hundreds of thousands of people is gone".
But he faced tough questioning from Mr Duncan Smith after Dr Reid's allegation that "rogue elements" were feeding journalists with false information about the government's approach to Iraq.
The Tory leader demanded to know who those "rogue elements" were.
"The whole credibility of his government rests on clearing up these charges," he said calling for an independent judicial inquiry.
"I simply say to the prime minister these allegations are not going to go away."
Lib Dem leader Charles Kennedy said: "Who are the public to trust if the government are letting it be known that they can't wholeheartedly trust their own intelligence
Former cabinet minister Robin Cook urged Mr Blair to acknowledge the government was mistaken in making the 45 minutes claim, and also the separate claim Iraq had tried to buy uranium from Africa.
Mr Cook later accused Dr Reid of "running around lighting bush fires" with his security services claims in the hope that attention would be diverted from the central charge.
Earlier, Dr Reid told BBC Radio 4's Today programme it was a "disgrace" that the integrity of the leadership of the security services was being impugned by "obviously rogue isolated individuals".
He urged critics to "put up or shut up" in the light of "15 years of evidence" that Saddam Hussein had weapons of mass destruction.
Intelligence and security committee is appointed by and reports to the prime minister, although it prides itself on its independence. It meets behind closed doors.
Foreign affairs committee is a cross-party select committee and meets in public.
MPs on the influential foreign affairs select committee are set to investigate the way the government presented intelligence information over Iraq's weapons.
The Intelligence and Security Committee inquiry will take place behind closed doors.
But the prime minister said its report would be published and his spokesman indicated that Mr Blair himself could give evidence to the inquiry.