In order to address the accusation, one must first know the actions, which you describe, and what information this was done to. Watch closely: You will see a lot of "he lied about Iraq", with very very few examples given.
To justify the attack on Iraq, one needs to know the following: Iraq signed a ceasefire agreement, in which the government was allowed to continue to exist if they complied with several terms. These terms included documentation and presentation of all WMDs to an inspection team for verified destruction. No serious nation, nor the U.N., nor even Hans Blix has claimed that Iraq complied with this.
Further, every serious government has conceded or stated that Iraq was seeking to hide and deceive in regards its compliance.
Further, Iraq had admitted to large quantities of WMDs, and had not turned them over for verified destruction.
By the way, in regards the chemical and especially biological warfare materials, have you calculated the volume required to store such materials? As example, a standard 10' x 12' bedroom is sufficient to hold 27,000 liters. How many chem or bio warheads is that - and we've found a smattering of specialized warheads suitable for such use. We've also found quite a number of "dual use" facilities, designed in an odd manner so that they can produce mundane things other than bio or chem agents, but could clearly be converted.
So other than that Nigerian(?) Uranium fraud, what actual accusation is there, beyond the vaguery that someone in the administration lied about something related to Iraq?