British Prime Minister David Cameron and opposition Labour leader Jeremy Corbyn clashed in parliament over whether former Labour prime minister Tony Blair misled parliament on the intelligence used to justify his decision to invade Iraq in 2003.
Cameron said the government must "learn the lessons" of Wednesday's Chilcot report on Britain's decision to join the US-led invasion of Iraq, and promised a two-day parliamentary debate on it next week.
But he said the report did not show that people were deliberately misled before the decision to invade Iraq.
"At no stage does he [Chilcot] explicitly say that there was a deliberate intention to mislead," Cameron told parliament.
Corbyn insisted that parliament was "misled" when a majority voted to approve the invasion. He said an "overwhelming weight of international legal opinion" found the invasion was illegal.
It was "not in any way a last resort" but was "an act of military aggression," said Corbyn, a long-term critic of Blair's role in taking Britain to war in Iraq.
"It led to the death of hundreds of thousands of people," Corbyn said, adding that it also caused millions of refugees, destabilized the region and fuelled terrorism.
"By any measure, the invasion and occupation of Iraq has been, for many, a catastrophe," he said.
"The decision to invade Iraq in 2003 on the basis of what the Chilcot report calls 'flawed intelligence' about the weapons of mass destruction has had a far-reaching impact on us all."
Cameron said taking a country to war "should only be a last resort and should only be done if all credible alternatives have been exhausted."
But he said it would be "wrong to conclude that we should not stand with our American allies when our security is threatened" or that "intervention is always wrong."