No it wasn't. It was an honestly held belief at the time. 9/11 affected the level of acceptable risk in Washington. We know Saddam had WMDs, we just didn't believe he'd gotten rid of them. They truly believed they would find them.
Only the 45 min claim was a gross distortion and subtle deception.
The fact is that we were lied to, in a huge propaganda campaign instigated by Bliar so that he could continue to crawl up shrubs arse, and make a few more millions out of his contacts.
The US tried to tell us that Hussein had WMD's, but neglected to tell us they had given them to him during the war with Iran.
The truth was that he had no delivery systems, that he had got rid of his arsenal during and after GW1, and had used the remaining arsenal to gas the Kurds.
The US, UK and every man and his dog knew this, but it was only necessary to convince the people in the street who are known as "sheeple" and are vital to any PR regarding any war.
So first they spoke about Iraq support for Al Qaeda and OBL (no evidence) and then they spoke of WMD and an "Axis of Evil"
The true reason for this "Axis of Evil" was that both Iraq and Iran had stopped using petro-dollars to trade oil, and then NK was thrown in for good measure as the "communist" bogeyman.
You only have to look at what happened to Gaddafi when he started speaking about no longer trading in petro dollars, and this will CONTINUE to happen.
It's known colloquially in foreign office circles as "Protecting UK interests abroad" which these days means licking US arses (politically) and saying "How High" when they say "Jump"