Campbell lays bare Blair's promise to Bush

Former PM's communications chief reveals explosive correspondence between leaders

Britain was committed to joining the United States in military action in Iraq in a series of secret letters sent to President Bush from Tony Blair months before the invasion, it has been revealed.

The contents of the notes, which were written by the former Prime Minister and only seen by a small group of senior ministers and advisers, were revealed for the first time at the Iraq inquiry yesterday as it heard from Mr Blair's head of communications, Alastair Campbell. In the correspondence, described as "very frank", Mr Campbell said that President Bush was given the overriding message that British troops would be beside their US counterparts in any invasion, should Saddam Hussein continue to defy the disarmament demands issued by the United Nations.

"I would say the tenor of them was that... we share the analysis, we share the concern, we are going to be with you in making sure that Saddam Hussein is faced up to his obligations and that Iraq is disarmed," Mr Campbell said. "If that cannot be done diplomatically and it is to be done militarily, Britain will be there."

During his grilling by the inquiry, which spilled over into an extra session, Mr Campbell launched a staunch defence of the decision to go to war in Iraq and the Government's case for the invasion, asserting that Britain should be proud of removing Saddam and what has been achieved since his departure. While he said that Mr Blair's instincts had always told him to back the US in any action it took, he had remained eager to find a peaceful resolution right up until a Commons vote on military action days before troops moved in.

In a typically combative display, Mr Campbell said he defended "every word" of the controversial September 2002 dossier, which set out Mr Blair's reasons for backing an invasion of Iraq and denied that he had "beefed up" any of its claims. The document suggested it was "beyond doubt" that Saddam possessed weapons of mass destruction (WMD) and that his weaponry could be launched within 45 minutes.

The former spin-doctor, who acquired an infamous reputation for confronting journalists over stories, said he had never been obsessed with headlines. He added that he had felt no compulsion to correct confused media reports that the now notorious 45-minute claim referred to weapons that could be used against other countries.

He denied that he had undue influence over the September document, which had been overseen by the Government's intelligence chief, Sir John Scarlett, adding that it was Sir John who was "100 per cent" in charge. "At no time did I ever ask him to beef up, to override, any of the judgements that he had," he said. "The whole way through, it could not have been made clearer to everybody that nothing would override the intelligence judgements and that John Scarlett was the person who, if you like, had the single pen."

But he admitted suggesting alterations to the document, as well as chairing two meetings with intelligence staff on how the dossier should be presented. He also admitted to drafting Mr Blair's foreword to the document, but denied that he had overstated that Saddam's WMD capabilities were "beyond doubt".

"If John Scarlett or any of his team had had any concerns of real substance about the foreword, then they know they could have raised those directly with the Prime Minister," he said. "I don't believe that if any of the [Joint Intelligence Committee] thought that the foreword in any sense over-stated the case to a degree that would impact the work that they had done – hit its credibility – they didn't feel they had the opportunity to say something." The assertion appeared to contradict Sir John's own evidence, during which he told the inquiry that he felt he could not substantially alter the foreword as he regarded it as "overtly political".

Meanwhile Mr Campbell also attacked Sir Christopher Meyer, the former British ambassador in Washington, for suggesting that Mr Blair had "signed in blood" a deal to back regime change during a meeting in Crawford, Texas, in April 2002. He turned on Clare Short, who resigned from the Cabinet soon after the invasion, saying she was not liked by senior military figures.

He also reopened an old feud with the media over its coverage of the Government's case for war in Iraq. He maintained that controversy only arose after the publication of "dishonest journalism" over the issue.

But last night Andrew Gilligan, the former BBC reporter at the centre of No 10's battle with the media, stood vehemently by his claim made in 2003 that Mr Campbell's involvement led to the "sexing up" of the dossier. "The documentary evidence shows that Campbell did pressurise John Scarlett particularly in regards to the nuclear issue," he told The Independent. "That was subsequently changed, remains unsupported by intelligence and is a sexing-up to me."

The evidence also put Gordon Brown in the spotlight, suggesting that the then Chancellor was central in discussions on Iraq. "I would say, certainly, that Gordon Brown would have been one of the key ministers who he spoke to," Mr Campbell said. It immediately led to calls for Mr Brown to be forced to give evidence to the inquiry ahead of the next election. The inquiry team has allowed him to delay his appearance until after a ballot.

In a rare moment of contrition, Mr Campbell conceded that a second dossier on Iraq, produced in February 2003, had been a mistake which damaged public trust. The document, which became known as the "dodgy" dossier, contained information taken from a journal on the Middle East.

Summing up his five hours of evidence, Mr Campbell said that at one time he thought Mr Blair would not survive the fallout from the invasion and could lose the 2005 election. But he said he remained proud of his role in the action taken against Saddam and said Britain should be, too. "I was privileged to be there and I'm very proud of the part I was able to play," he said.