A second key British general has criticised US post-war policy in Iraq.
Maj Gen Tim Cross said Donald Rumsfeld ignored warnings
Maj Gen Tim Cross, who was the most senior UK officer involved in post-war planning, told the Sunday Mirror US policy was "fatally flawed".
Maj Gen Cross said: "We were all very concerned about the lack of detail that had gone into the post-war plan."
His comments came after Gen Sir Mike Jackson, head of the Army during the invasion, told the Daily Telegraph US policy was "intellectually bankrupt".
The Ministry of Defence played down the comments by Sir Mike, now retired, saying he was entitled to express his opinion on his former job.
'Lack of detail'
In an interview published on Saturday, Sir Mike said a claim by the then US defence secretary Donald Rumsfeld that US forces "don't do nation-building" was "nonsensical".
Maj Gen Cross, also retired, said he had raised serious concerns about potential post-war problems in Iraq with Mr Rumsfeld as well.
But he said Mr Rumsfeld "dismissed" or "ignored" the warnings.
"Right from the very beginning we were all very concerned about the lack of detail that had gone into the post-war plan and there is no doubt that Rumsfeld was at the heart of that process," he said.
"I had lunch with Rumsfeld in February in Washington - before the invasion in March 2003 - and raised concerns about the need to internationalise the reconstruction of Iraq and work closely with the United Nations."
Maj Gen Cross, 59, who was deputy head of the coalition's Office of Reconstruction and Humanitarian Assistance, said he also raised concerns over the number of troops available to maintain security in Iraq.
"He didn't want to hear that message," he said. "The US had already convinced themselves that following the invasion Iraq would emerge reasonably quickly as a stable democracy."
He added: "There is no doubt that with hindsight the US post-war plan was fatally flawed and many of us sensed that at the time."
Politicians from across the spectrum have come out in support of Sir Mike's comments, made ahead of the serialisation of his autobiography in the Telegraph.
Sir Malcolm Rifkind, Conservative former foreign secretary and defence secretary, told the BBC that Mr Rumsfeld was "incompetent".
Shadow foreign secretary William Hague said the retired generals' criticisms re-enforced the case for a full inquiry into the war and its consequences, and called for a report to be made to parliament in October.
Mr Hague told Sky News: "We do think there have been many mistakes made. We would like to see a full-scale inquiry.
"I think some of the comments from one or two of the retired generals very much do strengthen the case for that and we want to see a full report when it gets back on Iraq."
A Downing Street spokesman said there had already been three "pretty exhaustive" inquiries, and that the prime minister had recognised there were lessons to be learned.
But he said that the process needed to wait until the fighting was over.
John Bolton, former US Ambassador to the UN, told BBC Radio 4's PM programme that Sir Mike had "read into a version of history that simply is not supported by the evidence".
"And I can see where he'd have a parochial view from the military perspective. I don't think he saw some of the larger political debates.
"I'm not saying that we got it right in Washington because I've made my own criticisms. His just happen to be way off the mark, very simplistic, I think in a sense limited by the role that he had."
The Telegraph also reports that, in his autobiography, Sir Mike says the US approach to fighting global terrorism was "inadequate" as it focused on military power rather than diplomacy and nation-building.
The US Department of Defence said: "Divergent viewpoints are a hallmark of open, democratic societies."
A spokeswoman for the US State Department said she would not comment on Sir Mike's views.
His comments follow a series of critical remarks from US officials about the British attitude towards Iraq.
BBC defence correspondent Paul Wood said Sir Mike's comments may put further strain on the British-US operation in Iraq.