The information to the Central Intelligence Agency (CIA) came from relatives of Iraqi scientists, the New York Times reported on its website late on Monday.
Citing unnamed government officials, the newspaper said the existence of a secret prewar CIA operation to debrief relatives of Iraqi scientists - and the agency's failure to give their statements to the president and other policymakers - has been uncovered by the Senate Select Committee on Intelligence.
The panel has been investigating the government's handling of prewar intelligence after US and British troops failed to uncover any alleged stockpiles of chemical and biological weapons the Bush administration used to justify the invasion.
The report, which is expected to be released this week, will likely contain a scathing indictment of the CIA and its leaders for failing to recognise that the evidence they had collected did not justify their assessment that Saddam Hussein had illicit weapons, the report said.
CIA reports on alleged Iraqi
WMDs were not accurate
CIA officials played down the significance of the information, saying only a handful of relatives made claims that the weapons programmes were dead, according to The Times.
The Senate report concludes that the agency and the rest of the intelligence community did a poor job of collecting information about the status of Iraq's weapons programmes.
Analysts at the CIA and other intelligence agencies did an even worse job of writing reports that accurately reflected the information they had, the paper said.
The document cites instances in which analysts may have misrepresented information, writing reports that distorted evidence in order to bolster their case that Iraq did have chemical, biological and nuclear programmes, according to the report.
The Senate found, for example, that an Iraqi defector who supposedly provided evidence of the existence of a biological weapons programme had actually said he did not know of any such thing, The Times said.
On whether a shipment of aluminium tubes seized on its way to Iraq was evidence that Baghdad was trying to build a nuclear bomb, the Senate panel wondered whether the CIA had become an advocate, rather than an objective observer, as it selectively sought to prove that the tubes were for a nuclear weapons programme.
But the committee has not found any evidence that the analysts changed their reports as a result of political pressure from the White House, according to The Times.