Tutu, a Nobel peace prizewinner and hero of the anti-apartheid movement, accuses the former British and US leaders of lying about weapons of mass destruction and says the invasion left the world more destabilised and divided "than any other conflict in history".
Writing in the Observer, Tutu also suggests the controversial US and UK-led action to oust Saddam Hussein in 2003 created the backdrop for the civil war in Syria and a possible wider Middle East conflict involving Iran.
"The then leaders of the United States and Great Britain," Tutu argues, "fabricated the grounds to behave like playground bullies and drive us further apart. They have driven us to the edge of a precipice where we now stand – with the spectre of Syria and Iran before us."
But it is Tutu's call for Blair and Bush to face justice in The Hague that is most startling. Claiming that different standards appear to be set for prosecuting African leaders and western ones, he says the death toll during and after the Iraq conflict is sufficient on its own for Blair and Bush to be tried at the ICC.