Giving evidence at the Chilcot Inquiry, she accused the former British prime minister of personally "conning" her, and of "deceiving" cabinet, parliament and the public. Ms Short claimed that Mr Blair broke the ministerial code by misleading parliament.
She accused Lord Goldsmith, the former attorney general who gave the "green light" to war, of failing to tell ministers the truth about his reservations over the legality of an invasion.
"I think he misled the cabinet," she said. "He certainly misled me. I think for the attorney general to come and say there's unequivocal legal authority to go to war was misleading."
When she tried to question the legal case for war in cabinet, Ms Short said she was jeered at and Mr Blair told her to "be quiet". Mr Blair's so-called sofa government meant that ministers had "little chats" rather than "substantive discussions". She said: "In the case of Iraq, there was secretiveness and deception."
Ms Short claimed she was "frozen out" despite being responsible for planning for the aftermath of any invasion.
On the eve of war, Ms Short decided to resign in protest at the failure to secure United Nations support. But she was talked round by Mr Blair who, it was claimed, did not want her to quit on the same day as the late Robin Cook, the leader of the House at the time. Two months later, she realised she had been "conned" by Mr Blair, who had assured her that he had persuaded George Bush to involve the UN in post-conflict planning.
She resigned in May 2003 in protest at the "feeble" UN resolution approving aid for Iraq.
In a stinging attack, she claimed Mr Blair ignored warnings that the military and aid officials were not ready for war because he was "frantic" to support US President George Bush.
Over three hours of evidence, Ms Short told the inquiry Mr Blair ignored the cabinet's views and made the decision to invade Iraq secretly with his "mates".
She said: "I'm not saying he was insincere. I think he was willing to be deceitful about it because he thought it was right."
The former international development secretary said the machinery of Government had "broken down quite badly" under Mr Blair, who appeared before the inquiry last week.
Ms Short said: "I noticed Tony Blair in his evidence to you kept saying, 'I had to decide, I had to decide'. And indeed that's how he behaved. But that is not meant to be our system of government.
"When you add secrecy and deceit, the system becomes positively dangerous."
Ms Short was damning about Mr Blair's failure to ask Washington to delay the invasion so military commanders and humanitarian agencies could be better prepared and to allow weapons inspectors more time to search Iraq for weapons of mass destruction.
She said: "I think he was so frantic to be with America that all that was thrown away.
"We have made Iraq more dangerous as well as causing enormous suffering and diminishing our reputation," she told the inquiry.
Ms Short stood down from the cabinet on May 12, 2003, nearly eight weeks after the invasion. She now sits as an independent MP.
She was applauded by the audience in the inquiry chamber in central London after finishing her evidence. (©Daily Telegraph, London)