Former Prime Minister Paul Keating has called for John Howard to "hang his head in shame" over his involvement in the Iraq War, which he says brought "the spectre of terrorism and racial strife" to Australia.

Mr Keating, a Labor Prime Minister who served for two terms and was succeeded by Mr Howard in 1996, said Mr Howard should "atone for his actions and those of his government" after a UK government report found the 2003 invasion of Iraq was based on flawed intelligence.

The Chilcot report, released on Wednesday, found the flawed intelligence should have been challenged but wasn't, and the severity of the threat posed by Iraq's "weapons of mass destruction", which were never found, was presented to the public with "a certainty that was not justified".