MP George Galloway has said it could be "morally justified" to assassinate Tony Blair, but stressed he was not calling for his death.
In an interview with GQ magazine he was asked whether a suicide bomb attack on Mr Blair would "be justified as revenge for the war on Iraq".
He said it would be morally equivalent to Mr Blair "ordering" Iraqi deaths.
But Mr Galloway said he would not support an attack and would tell the authorities if he knew of any plot.
Alert the authorities?
In the interview, former Daily Mirror editor Piers Morgan asked: "Would the assassination of, say, Tony Blair by a suicide bomber, if there were no other casualties, be justified as revenge for the war on Iraq?"
The Respect MP replies: "Yes it would be morally justified. I am not calling for it, but if it happened it would be of a wholly different moral order to the events of 7/7.
"It would be entirely logical and explicable, and morally equivalent to ordering the deaths of thousands of innocent people in Iraq as Blair did."
No politician, ever, by act, word, or deed should give any support to the notion that violence might be justified
Sir Menzies Campbell
Lib Dem leader
He was also asked whether he would alert the authorities if he knew Mr Blair was to be assassinated by Iraqis.
Mr Galloway replied: "My goodness this is a moral maze.
"Yes, I would, because such an operation would be counterproductive because it would just generate a new wave of anti-Muslim, anti-Arab sentiment whipped up by the press.
"It would lead to new draconian anti-terror laws, and would probably strengthen the resolve of the British and American services in Iraq rather than weaken it. So yes, I would inform the authorities."
War crimes appeal
Mr Galloway is standing by the controversial comments.
In a statement, the MP said: "Like the prime minister's wife commenting on suicide bombings in Israel I understand why such desperate acts take place and why those involved might believe such actions are morally justifiable.
"From the point of view of someone who has seen their country invaded and their family blown apart it's possible, of course, for them to construct a moral justification.
"But I've made my position clear. I would not support anyone seeking to assassinate the prime minister.
"That's why I said in the interview I would report to the authorities any such plot that I knew of.
"What I did make abundantly clear to Piers Morgan in the GQ interview is that I would like to see Tony Blair in front of a war crimes tribunal for sending this country to war illegally and for the appalling human consequences which resulted. That's what I will continue to press for."
Later, Mr Galloway told BBC Radio 4's PM he wanted to see "mass murderer" Mr Blair jailed for life for war crimes rather than killed.
But he said Iraqis had a right to resist the illegal occupation of their country.
He asked: "Why would that right be restricted to the poor bloody infantry that Mr Blair sent into the streets of Iraq?"
Downing Street has refused to comment on Mr Galloway's remarks.
But Liberal Democrat leader Sir Menzies Campbell condemned the comments.
"If Mr Galloway is being accurately reported, he could well be regarded as providing encouragement to someone who might be disposed to carry out a crime of that kind," said Sir Menzies.
"No politician, ever, by act, word, or deed either expressly or by implication, should give any support to the notion that violence might be justified."
Labour MP Stephen Pound told The Sun newspaper the remarks were "disgraceful".
He said: "Every time you think he can't sink any lower he goes and stuns you again. It's beyond reprehensible to say it would be justified for a suicide bomber to assassinate anyone."
Mr Galloway has been in Cuba this week, where he made a surprise appearance on live television alongside Fidel Castro.
bizzarre. even i think it's a cunt thing to say.
yet, i kinda agree. blair caused deaths of iraqis. it's hard to say retaliation against the person who lied so he could go into a war that killed 1000s, against the wishes of his own people wouldn't be justified