Mr John Kerry has renewed his call for Defence Secretary Donald Rumsfeld's resignation and said the official investigation into abuses at Iraq's Abu Ghraib prison demonstrated a failure of civilian leadership.
"It's about leadership and it's about accountability," the US Democratic presidential nominee told supporters at a Philadelphia steamfitters' union hall where he spoke before travelling to Wisconsin.
John Kerry
Americans "want the truth and they want accountability," he said.
A report issued on Tuesday by an independent four-member panel headed by former defence secretary James Schlesinger showed there was a "failure of the civilian chain of command," the Democratic presidential challenger said.
"It's not just the little person at the bottom who ought to pay the price . . . the buck doesn't stop at the Pentagon," he said.
Mr Kerry did not mention Mr Bush by name, but he said the prison-abuse scandal was part of a larger failure involving miscalculations about the troop strength needed in Iraq and the costs involved.
He said Mr Rumsfeld should resign "for failure to do what he should have done" and said Mr Bush should conduct his own investigation into the decision making that led to the penal abuses.
Mr Kerry called in May for Mr Rumsfeld's resignation over the abuse scandal and said at the time he had urged Mr Rumsfeld to quit months earlier due to miscalculations on Iraq.
White House spokesman Scott McClellan dismissed Kerry's comments as his "latest political attack."
The Schlesinger report said top Pentagon civilian and military leaders and the military command in Iraq contributed to an environment in which prisoners suffered sadistic abuse at Abu Ghraib.
It found Mr Rumsfeld and the Joint Chiefs of Staff failed to exercise proper oversight over confusing detention policies at US prisons in Iraq and Afghanistan.