Gordon Brown is not just difficult to work with, but "impossible", according to Bob Ainsworth, the former defence secretary.
Ainsworth, who helped lead Britain's military commitment in Afghanistan, said he found it difficult to get one-to-one meetings with the prime minister and his views on defence policy were ignored.
The revelations are damaging to Brown who has always maintained that he ran a collective leadership over Afghanistan.
In his first interview since the election defeat Ainsworth told the Birmingham Post: "It's no secret that Gordon and I are not each other's greatest fans. I found him very difficult to work with. Impossible really."
He also said he took the post of defence secretary in June last year believing it would be for only 11 months because he assumed Labour would lose the election.
Ainsworth said the greatest difficulty in his relationship with Brown occurred last October when an official inquiry was published into the death of 14 servicemen who died when an RAF Nimrod surveillance aircraft burst into flames over Afghanistan. The inquiry report by Charles Haddon-Cave QC exposed catastrophic design faults in the Nimrod MR2 which were not put right as a result of cost-cutting and "complacency".
Ainsworth said Brown demanded the grounding of the entire Nimrod fleet even though repairs to the relevant faulty hot-air ducts and fuel pipes on the remaining aircraft had taken place. Ainsworth took the view that the aircraft were safe to fly, but Brown disagreed because he wanted to be seen to be tough. "He wanted me to ground the fleet. I said if you give me a written order I will do so, but not unless," said Ainsworth.
Referring to Brown's leadership style, Ainsworth said: "You have to pay a price if you want people to be part of a team. There has to be discussion.
"You have to be given a day in court there has to be conversation. You have to be given a chance to promote your bid, but with Gordon so often you don't."
Ainsworth is the latest senior Labour figure to openly criticise Brown. The former prime minister is coming under increasing attack in the Labour leadership election with candidates revealing a range of disagreements.
Ainsworth said he was also frustrated at public attitudes to defence spending. "We want to be an important country, but we don't want to pay for defence," he said. "That's not just a Labour party issue it affects the Tories and Liberal Democrats as well. We are spending more than most European countries on defence as a proportion of GDP.
"The big dilemma is, and this annoys me more than anything that people will look at the television and say something must be done but they won't pay for the means to do it."
Ainsworth said that the former government had tried but failed to explain to the public the reasons for Britain's involvement in Afghanistan. He said: "The biggest issue is that the overwhelming majority of the people in this country do not get Afghanistan. They don't believe us when we say national security is at stake. But it is not for lack of trying, we have tried to put the case. We in the west walked away from Afghanistan at the end of the cold war and left it as a country devastated socially and armed to the teeth. If we do that again there will be consequences."