The head of the Armed Forces at the time of the 2003 invasion accused the Prime Minister of being "disingenuous" in saying that he provided military chiefs with everything they asked for.
While he expressed "regrets" over the failure to plan properly for the aftermath of the invasion, Mr Brown today strongly rejected allegations that, as Chancellor of the Exchequer, he had failed to provide the forces with the resources they needed.
Giving evidence to the Chilcot Inquiry into the war in Iraq, Mr Brown insisted: "Every request that military commanders made to us for equipment was answered. No request was ever turned down."
But Admiral Lord Boyce, the Chief of the Defence Staff up to the start of the invasion of Iraq in 2003, challenged Mr Brown's claim.
"He's dissembling, he's being disingenuous," Admiral Boyce told The Times.
"It's just not the case that the Ministry of Defence was given everything it needed. There may have been a 1.5% increase in the defence budget but the MoD was starved of funds."
Mr Brown began and ended his four hours of testimony by paying tribute to the 179 British servicemen and women who lost their lives in the conflict, while acknowledging the "huge" death toll among Iraqi civilians.
Although Britain and the United States had acted for the "right reasons" he said, it was important lessons were learned.
"Obviously the loss of life is something that makes us all sad. We have got to recognise that war may be necessary, but it is also tragic in the effect it has on people's lives," he said.
"These were difficult decisions, these were decisions that required judgment, these were decisions that required strong leadership, these were decisions that were debated and divided a lot of opinion in the country.
"I believe they were the right decisions for the right reasons but I also believe it is our duty to learn the lessons from what has happened.
"No one who makes the decisions that Cabinets and governments have to make can do so without recognising that lives are affected and sometimes lives are lost as a result of the big decisions and the big challenges we have got to meet."
Mr Brown said he had been kept "fully informed" about developments in the build-up to the invasion in March 2003 but at the same time he made clear that he was not central to the decision-making process.
He said he was not involved in the discussions ahead of Mr Blair meeting then US president George Bush at his ranch in Crawford, Texas, in April 2002 - where Mr Blair made clear Britain would join any military action - and he did not see Mr Blair's private correspondence with the president.
However he said that he had consistently argued in Cabinet that military action should only be used as last resort once all the diplomatic avenues to find a peaceful resolution had been exhausted.
Mr Brown insisted that throughout he had given the military the resources it needed for the campaign, providing an additional £8 billion since 2002 on top of a rising "core" defence budget.
"I said immediately to the Prime Minister that the military options that were under discussion, there should be no sense that there was a financial restraint that prevented us doing what was best for the military," he said.
"At any point, commanders were able to ask for equipment that they needed and I know of no occasion when they were turned down."
He acknowledged the concerns of the families of soldiers killed travelling in lightly armoured Snatch Land Rovers, but insisted the choice of the equipment used on particular operations was a matter for the military.
When the Ministry of Defence asked for better protected vehicles in 2006, he said he provided £90 million to enable the purchase of 150 Mastiff and Bulldog armoured vehicles.
"That was a decision that military commanders could make only themselves. But once these new vehicles were asked for, they were offered and the money was paid, I think within months," he said.
He also defended the decision to curb defence spending following the invasion in 2003, after the MoD used new Whitehall accounting rules to claim that it had found £1.3 billion in efficiency savings to spend on new equipment.
"If we had had every department doing what the Ministry of Defence was doing, we would have had the extra cost of £12 billion which would be the equivalent of raising income tax by 3p in the pound," he said.
Major General Tim Cross, who was Britain's most senior officer in the reconstruction effort following the invasion, agreed that Mr Brown had funded the Urgent Operational Requirements (UORs) for additional kit requested by commanders on the ground, but questioned his wider support for the armed forces.
Gen Cross told BBC2's Newsnight: "What Gordon Brown is responding to is that the UORs that were asked of the Treasury were funded by the Treasury. What I think most people are talking about is a much broader issue of defence spending in the round from 1997/98 through to 2003, 2004 and 2005.
"I think he is talking about UORs, which he didn't turn down. The Treasury didn't refuse any of our UORs.
"What he had refused and what had been a bone of contention for some time is a much broader issue of the level of defence spending in the round.
"The defence planning assumptions were being broken year after year after year."
Lord Boyce's criticism of the Prime Minister was echoed by another former Chief of Defence Staff, General Lord Guthrie of Craigiebank.
Lord Guthrie, who led the armed forces from 1997-2001, told the Daily Telegraph: "To say Gordon Brown has given the military all they asked for is simply not true.
"He cannot get away with saying 'I gave them everything they asked for', that is simply disingenuous."
Comments