Former Labor leader Simon Crean has said there is a "strong causation" between the controversial 2003 Iraq invasion and the immediate terrorism threat that Australia faces today.

Mr Crean, who led Labor when it opposed the invasion, told Fairfax Media on Friday that then prime minister John Howard had "gone to war on a lie".

His broadside followed a scathing assessment by former prime minister Paul Keating of Mr Howard's decision to send troops, and adds to a list of senior Labor figures who have savaged Mr Howard's decision.

Mr Crean dismissed Mr Howard's claim following the release of a damning British report into the Iraq war that critics were enjoying the benefit of hindsight.