The 2.5 million word Chilcot report, detailing Mr Howard's role in the war, resoundingly and categorically rejected former British Prime Minister Tony Blair's decision to join the US-led conflict.
Commenting on words exchanged between Blair and Bush at Camp David, US later that year, the Chilcot report adds: "Although at that stage no decision had been taken on which military package might be offered to the US for planning purposes, Mr. Blair also told President Bush that, if it came to war, the United Kingdom would take a significant military role".
New Zealand has twice chose to deploy troops to Iraq following the 2003 invasion, and both decisions were politically fraught.
"What I can not do, and will not do, is say we took the wrong decision", he said, insisting that the world was "a better place" after the fall of Saddam Hussein's regime.
"I will at the same time say why, nonetheless, I believe that it was better to remove Saddam Hussein and why I do not believe this is the cause of the terrorism we see today whether in the Middle East or elsewhere in the world", he added.
Prime Minister John Key says his support for the Iraq war in 2003 was based on the information he and others had at the time.
Arguments have been ongoing since 2003 over whether or not the invasion was legal and whether or not parliament was misled ahead of taking the vote on whether or not to take military action.
In an emotional press conference, Tony Blair took full responsibility and apologized.
In the report, Mr. Blair emerges as not just an obedient junior ally of the then U.S. President George W. Bush, but as a powerful backer and, sometimes, a step ahead of the U.S. President, first in pushing for regime-change in Iraq, and then endorsing military invasion as a means to carry it out.
√ No support for Blair critics' claim that he agreed a deal "signed in blood" to topple Saddam with US President George W Bush in April 2002.
Blair was warned about the threat of increased al Qaeda activity as a result of the invasion, the report said.
"I am not going to be harsh about Tony Blair, he has destroyed his own reputation".
The former premier has made a series of media appearances since the Chilcot Report's publication on Wednesday in an attempt to explain the decision which has come to define his time in office.
He said he felt "more sorrow, regret and apology than you may ever know" for the grief of those whose loved ones died.
"I will take it up with whoever is the next Prime Minister", Wilkie told media in Melbourne.
The former British leader's legacy as a three-times election victor for the center-left Labour Party has been overshadowed by years of accusations that he had lied to exaggerate the intelligence case for war.
But the world isn't safer in Baghdad, as last weekend's devastating bombing again showed, and it's not better for the families of the British soldiers who died in Iraq.