"Obviously the war in Iraq was a big, fat mistake," Trump said, launching into a fierce critique of rival Jeb Bush's brother.

"George Bush made a mistake," the billionaire continued. "Obviously we can make mistakes, but that one was a beauty."

"We should have never been in Iraq," Trump added. "They lied, they said there were weapons of mass destruction. There were none and they knew that there were none."

Jeb Bush aggressively defended his brother.

"I'm sick and tired of Barack Obama blaming my brother for all the problems that he's had and frankly I could care less about the insults Donald Trump gives against me," the former Florida governor said.