LONDON, England -- Former British Prime Minister Tony Blair's one-time media adviser was appearing Tuesday at an inquiry into the country's involvement in the Iraq war -- the most prominent figure yet to testify at the proceedings.

Alastair Campbell was Blair's communications director, often called his spin doctor, and he managed the British government's case for war in Iraq.

In the first hour of his testimony, Campbell stressed that Blair was determined to disarm Iraqi leader Saddam Hussein, but that he had never been in a "rush to war" and regarded military action only as a last resort.

"Was the regime part of it? Of course. Would someone like Tony Blair, from the day he went into politics, think that somebody like Saddam Hussein should be got rid of? Yes, he would. Was that the policy he was pursuing the whole way through? No," Campbell told the inquiry.

"He was trying to, through the (United Nations), lead the British government in the direction of pursuing a policy that would lead ultimately to disarmament of Saddam Hussein," Campbell said of Blair.

When it became clear that the diplomatic process was not going to work, he added, that's when Blair opted for military action.

Inquiry members were asking Campbell about his involvement in a government intelligence dossier that detailed the threat posed by Iraq. The dossier said Saddam Hussein was capable of launching weapons of mass destruction within 45 minutes of giving an order -- a claim that has never been proven.

In May 2003, a BBC report accused the government, and Campbell in particular, of pushing for the dossier to be "sexed up" to exaggerate the Iraqi threat.

The inquiry, which began hearings in late November, is the most thorough investigation yet into the decisions that led up to the war.

It cannot find anyone criminally responsible, and it cannot even apportion blame, but inquiry members will be able to judge the legality of the conflict and identify lessons learned from Britain's involvement.

Prime Minister Gordon Brown promised last year that the committee would have access to the full range of information about the war and the lead-up to it, including secret documents.

Inquiry Chairman John Chilcot has said Blair will be called to testify, and Blair has said he will appear.

Campbell may be asked about Blair's statement last month that he would have removed Saddam even without evidence of weapons of mass destruction in Iraq.

"I would have still thought it right to remove him," Blair told the BBC in an interview. "I mean, obviously you would have had to use and deploy different arguments about the nature of the threat."

Britain has held four other hearings about the Iraq war. But because all were held before the end of 2004 -- so close to the start of the war -- they were hampered by limited information, political analysts have said.

The current inquiry has the greatest potential to tell the "full story" of the decisions leading up to war, analyst Glen Rangwala of Cambridge University told CNN in November.