“I was struck by the force of the language in the American national intelligence assessment late in November 2002,” he told the Seven Network in an interview late on Sunday.

“It brought together all the American intelligence and paragraph after paragraph, they said, we judge Iraq has got weapons of mass destruction and even talked about potential nuclear capacity.”

“Now that wasn’t made up. It may have been an erroneous conclusion based on the available information but it wasn’t made up.”

No weapons of mass destruction were ever found in Iraq, undermining the basis for the conflict that left thousands of Iraqis and foreign soldiers dead.

“I felt embarrassed, I did. I couldn’t believe it because I had genuinely believed it,” Howard said.

“So, I felt embarrassed and I did my best to explain ... that it wasn’t a deliberate deception.”

Howard also said it was wrong to say that the Iraq conflict alone created Islamic State.

“So much of the Islamic State operation comes out of what is occurring in Syria and to suggest that it’s purely or predominately a result of what happened in Iraq in 2003 is a false reading of history,” he said.

But lawmaker Andrew Wilkie, a former intelligence officer, accused Howard of rewriting history, saying Australia’s own intelligence organisations had provided secret briefings to him that had explained US and British motives for war.

Australia’s intelligence had also cast doubt on whether Baghdad had the weapons, he said, making instead a compelling case that it had a disjointed and contained programme that was not a threat to the region, let alone Australia.

“It’s not good enough for John Howard to cherry pick one particular report and to hold that up as the evidence to use for him to rewrite history,” Wilkie told reporters on Monday.

He said there was no doubt the Islamic State group had emerged from the war.

“If we had not gone to war 11-and-a-half years ago ... then the circumstances would not exist for IS to have emerged and grown strong,” he said.