In a 80-page report, due to be presented to President Moshe Katsav later on Sunday, the subcommittee blamed the intelligence establishment for having exaggerated the threat of non-conventional weapons while ignoring the threat posed by Libyan nuclear projects.
The subcommittee, headed by foreign affairs and defence committee chairman Yuval Steinitz, is charged with monitoring the activity of Israel's secret services.
It spent eight months considering the intelligence agencies' performance on Iraq. A secret section is still in preparation.
A member of the parliamentary subcommittee that prepared the report said that Israeli intelligence ahead of the March 2003 invasion of Iraq was based on "assessments rather than hard information." He spoke on condition of anonymity.
Rumour as fact
The report said that such hearsay, sent to the United States for verification, was leaked to the Israeli media in the guise of fact.
Apparently, the information was recycled and accepted as fact by the Israeli government, it said. It was not immediately clear at what point rumours and speculation were presented as fact.
Israeli intelligence hyped up
the reasons for US-led invasion
The report says Israel's coordination with foreign intelligence agencies was faulty, said members of the panel of inquiry.
The subcommittee called for the implementation of far-reaching structural changes to the intelligence services.
It illustrated the need for change by highlighting two major intelligence failures - the assessment that Iraq possessed weapons of mass destruction, and the failure to identify that Libya had developed nuclear capabilities.
Four months ago, Israeli analyst Shlomo Brom published a report accusing the Israeli intelligence community of overstating the risk of an Iraqi attack.
"The intelligence services greatly exaggerated the risk of a non-conventional attack without daring to say that it was little or nil," Brom said.
"It goes without saying that exaggerating a threat is less dangerous than minimising a real risk but it is no less a mistake."
"The intelligence services greatly exaggerated the risk of a non-conventional attack without daring to say that it was little or nil"
In his report, Brom said the Israeli intelligence services had lost credibility with both their overseas counterparts and the public while also spending "a great deal of money on addressing threats that were either non-existent or highly unlikely."
Precautionary measures taken included the mobilisation of troops, the deployment of anti-missile defences and the distribution of millions of gas masks to the population.
All these were costly and completely unnecessary, the report said.
Several months before the US-led invasion, Israeli Prime Minister Ariel Sharon had warned the population of the risk of an Iraqi attack and said the country would take all necessary measures to counter it.
And at the tail end of the invasion, the head of military intelligence, General Aharon Zeevi, said there was "no doubt that Iraq has non-conventional weapons."