The row over the Bush administration's response to Hurricane Katrina has been stoked by the former US disaster chief, testifying to a Senate oversight panel.
Mr Brown testimony was at times confrontational
Former Fema chief Michael Brown said officials knew levees were breached in New Orleans much earlier than admitted but did not act swiftly enough.
Mr Brown criticised the Department of Homeland Security, which controls the Federal Emergency Management Agency.
He said DHS policies had put Fema on "a path to failure".
More than 1,300 people across five states were killed by the storm last August. Hundreds of thousands of people were displaced in its aftermath.
Mr Brown resigned as Fema chief in mid-September amid mounting criticism of the sluggishness of the disaster response.
His testimony came as a report in the New York Times, citing details of a Congressional investigation, said that an eyewitness account of the flooding from a federal emergency official reached the DHS headquarters at 9.27pm on 29 August, and the White House by midnight.
A day later, officials in the Bush administration were still expressing surprise when they were told that the levees had been engulfed.
Appearing before the Senate Homeland Security and Government Affairs committee, Mr Brown went far further than he had previously in blaming other elements of the Bush administration for the halting reaction to the storm.
Much of the damage caused by the hurricane remains untouched
He contradicted DHS officials who had said earlier they were unaware of the severity of the problems until the day after Katrina hit the Gulf Coast city.
Mr Brown said: "I find it a little disingenuous. For them to claim that we didn't have awareness of it is just baloney."
"There was a cultural clash which didn't recognise the absolute inherent science of preparing for disaster, responding to it, mitigating against future disasters and recovering from disaster," Mr Brown told the committee.
The BBC's Lesley Curwen, in Washington, says that what is emerging from the hearing is a sense of the bitter turf-war being fought between Fema and the DHS.
Mr Brown revealed that he had made it a practice to by-pass getting authority for his actions from the DHS, because of the bureaucracy involved - he said he preferred to deal directly with the White House instead.
And he argued that the response to Hurricane Katrina would have been more effective if a terrorist had blown up one of the levees.
Natural disaster, he said, had become the "step-child" in the Department of Homeland Security.
Earlier this month a report by the Government Accountability Office singled out Homeland Security Secretary Michael Chertoff for not taking control of the much-criticised relief effort.
The report's authors said delays in sending aid and assistance to the disaster zone could have been avoided by a swift appointment of a senior government figure to lead the response.