Former Cabinet minister Clare Short has likened insurgents in Iraq to the French resistance who battled the German occupation.
Ms Short said she understood the anger of Iraq's insurgents
The ex-international development secretary told Dubai-based Gulf News that "killing civilians is always wrong.. but I think the cause is just".
As the Americans fought British colonialism, so the Iraqis should be able to "resist occupation", she said.
Ms Short resigned her Cabinet post over the Iraq war in May 2003.
She told the newspaper she understood the anger of those who embraced Islamic militancy.
"My father came from Northern Ireland... and I understand why people think 'I can't get justice in any other way.'
"I think it's always wrong to target civilians... because when you understand the IRA, they never targeted civilians.
"That's the terrible moral deterioration that's taken place."
It was not good enough for the world to say "state violence is OK and non-state violence is not OK", she added.
Ms Short also argued the Palestinians were entitled under international law to "resist occupation" as Iraq's insurgents should be.
Ms Short also hit out at Tony Blair for the way he presented the case for the Iraq war.
He had "engaged in a whole series of half-truths and deceptions" to win backing for the military action, she said.
Mr Blair had already pledged to support George Bush before gaining Parliament's approval for the war, she alleged.
"At the same time he was telling his party, Cabinet, Parliament and the country that he wanted to avoid war, that we would proceed through the UN, that we were determined to get the implementation of the [Middle East] road map, he had already given his word to Bush," she said.
Samantha Roberts, the husband of the first British soldier to die in action in Iraq, Sergeant Steven Roberts, said she understood where Ms Short "was coming from".
"A civilian is an innocent party but military personnel know what their job is," Mrs Roberts said.
Tony Hamilton-Jewell, whose brother was killed by a mob as he manned an Iraqi police station, also suggested the insurgents were entitled to stand up for their beliefs.