The former prime minister Sir John Major yesterday mounted his strongest attack on Tony Blair over the Iraq war.
Sir John said evidence emerging in the Chilcot inquiry showed his successor's main motivation appeared to have been regime change – despite claims that it was to tackle Saddam Hussein's weapons of mass destruction.
He demanded to know whether cabinet members in 2002 and 2003 had been aware of the doubts over weapons of mass destruction, highlighted in evidence to the Chilcot inquiry, before military action was taken.
Mr Blair is preparing to give evidence to the body, most likely in February.
Sir John said the handling of Iraq had done more damage to trust in the UK political system than the expenses scandal. He said he had trusted Mr Blair's claims about the danger Iraq posed, but was now not so sure.
"The suspicion arises that this was more about regime change than it was about weapons of mass destruction," he told Radio 4's Today programme.
"The argument that Saddam Hussein was a bad man and had to be removed simply won't do.
"There are many bad men around the world who run countries and we don't topple them and, indeed, in earlier years we had actually supported Saddam Hussein when he was fighting against Iran.
"The argument that someone is a bad man is an inadequate argument for war and certainly an inadequate and unacceptable argument for regime change."
Sir John also said that in the mid-1990s aides to the then US President Bill Clinton had raised the idea of regime change in Iraq with UK officials. They had replied that any attempt to remove Saddam had to be legal and viable.