Two of the candidates attempting to become the next Labour leader have criticised the decision to invade Iraq.
Ed Balls, the former children’s secretary, told the Daily Telegraph the war was "wrong" and "a mistake".
And in an interview with the Guardian former energy secretary Ed Miliband said the way the decision to go to war was taken "led to a catastrophic loss of trust in Labour".
The result of Labour’s leadership contest will be known on 25 September.
The other candidates for leadership are Diane Abbott, Andy Burnham, John McDonnell and Ed Miliband’s brother, David, who was an MP at the time of the invasion of Iraq and voted for it.
Mr Balls said that, based on the information made available, "we shouldn’t have prosecuted the war".
He added: "We shouldn’t have changed our argument from international law to regime change in a non-transparent way. It was an error for which we as a country paid a heavy price, and for which many people paid with their lives.
"Saddam Hussein was a horrible man, and I am pleased he is no longer running Iraq. But the war was wrong."
Ed Milliband, the former energy and climate change secretary, said the basis for going to war was Saddam Hussein’s potential possession of weapons of mass destruction.
"Therefore that is why I felt the weapons inspectors should have been given more time to find out whether he had those weapons, and Hans Blix – the head of the UN weapons inspectorate – was saying that he wanted to be given more time," Mr Miliband said.
"The combination of not giving the weapons inspectors more time, and then the weapons not being found, I think for a lot of people it led to a catastrophic loss of trust for us, and we do need to draw a line under it."
Mr Miliband, who was not an MP at the time of the invasion of Iraq, said because the basis for the war "turned out not to be correct", the decision to prosecute it was "a big loss of trust for us".
He added: "What I am not saying is that the war was undertaken for the wrong motives but what I am very clear about is what my position was at the time and the way I look at it in retrospect."
The BBC’s Mike Sergeant said the race to ditch the baggage of the Blair/Brown years was moving on apace for Labour’s leadership contenders.
"For Labour members, the invasion of Iraq in 2003 remains one of the least popular decisions," our correspondent said.
Speaking in March at the Chilcot inquiry into the Iraq war, David Miliband said: "I voted for the war because I think that the defiance by Saddam of the UN was itself a danger to international peace and security and the authority of the UN had to be upheld."
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