Insisting that the country needed to start afresh on Iraq and seek wider alliances, the Democratic duo on Saturday alleged that the president broke promises and launched the invasion with undue haste.
Kerry said Bush had "pushed hard and distorted to create a framework for the intelligence they wanted and the outcome they wanted".
Speaking a day after a scathing Senate report condemned US intelligence agencies for faulty WMD claims, Kerry accused Bush of disinformation over Iraq's arsenal and al-Qaida connections.
The two defended their votes for the congressional authorisation allowing Bush to go to war, claiming instead that Bush had violated their trust.
Bush, they said, broke his promise to build "a true international coalition", honour the UN weapons inspection process and go to war only as a last resort.
"Based on the information we had the time that we had it, it was the right vote," Kerry said. "The problem is the president did not honour what he said he would do in the exercise of the authority that he was given."
"Not only that, he abused the authority," said Edwards, sitting next to Kerry.
Kerry declined to criticise countries such as France and Germany for their reluctance to help in Iraq.
"I think that it probably will take a new president to wipe the slate clean and offer the kind of leadership that has the potential to change the dynamics of what's happening in Iraq," Kerry said.
Edwards echoed similar sentiments, stating Bush was an obstacle in building a wider coalition.
"They are hungry, hungry for a positive relationship ... but the problem is the history with Bush."