Finally Tony Blair reveals his side of the feud with Gordon Brown

Tony Blair has described Gordon Brown as "maddening" and "difficult" when he was his Chancellor but has defended his decision not to sack him or try to stop him becoming Prime Minister.

In his memoirs, A Journey , to be published today, the former Prime Minister finally breaks his silence on the tension between him and Mr Brown which destabilised his 13 years as Labour leader.

In extracts from the book, Mr Blair accuses his successor of abandoning New Labour, arguing that it could have won this year's election if he had stuck with it. He writes: "So was he difficult, at times maddening? Yes. But he was also strong, capable and brilliant, and those were qualities for which I never lost respect."

On Iraq, he admits that many of his supporters see the war as "the stain" on an otherwise impressive record. But he says he cannot satisfy their desire for him to admit it was a "mistake" made in good faith. "Friends opposed to the war think I'm being obstinate; others, less friendly, think I'm being delusional," he admits.

Mr Blair concedes that the aftermath of the war was a "nightmare" and that Britain and the United States did not anticipate the role played by al-Qa'ida and Iran in post-war Iraq. But he insists that leaving Saddam Hussein in power was "a bigger risk to our security than removing him".

He explains why he did not say he had any regrets when he was asked if he had any by the Chilcot Inquiry in January. He describes it as a "headline question": if he had said Yes, the outcome would have been "Blair apologises for war" and "at last he says sorry".

Addressing his critics head-on, he writes: "Do they really suppose I don't care, don't feel, don't regret with every fibre of my being the loss of those who died?" He insists that he thinks about the victims of the wars in Iraq and Afghanistan every day of his life.

He says he cannot, by any expression of regret, bring to life those who died, but says he can dedicate a large part of his life to a wider struggle. "I can't say sorry in words; I can only hope to redeem something from the tragedy of death, in the actions of a life, my life, that continues still," he writes.

Until now, the former Prime Minister has kept to himself his views on the man he overtook to become the modernising candidate for Labour leader when John Smith died in 1994 and who bore a grudge against him ever since. He did not want to be accused of undermining Mr Brown after he stood down as Prime Minister in 2007.

The extracts reveal Mr Blair's disappointment at his successor's performance in 10 Downing Street. "It is easy to say now, in the light of his tenure as Prime Minister, that I should have stopped it; at the time that would have been well nigh impossible," he says.

If he had sacked or demoted his Chancellor, Labour and the government would have been "severely and immediately destabilised" and Mr Brown would probably have forced him out of Downing Street even faster.

Insisting that it was not because he lacked courage that he failed to sack Mr Brown, he writes: "I believed, despite it all, despite my own feelings at times, that he was the best chancellor for the country."

Although he claims Mr Brown resisted and slowed down some of his public service reforms, Mr Blair argues that his Chancellor did not prevent them and that major changes were implemented. He admits the "relentless personal pressure" from Mr Brown, who repeatedly asked him when he would stand down as Prime Minister, was "wearing".

Mr Blair says he concluded it was better to keep Mr Brown inside the tent. "I came to the conclusion that having him inside and constrained was better than outside and let loose or, worse, becoming the figurehead of a far more damaging force well to the left."

He praises Alastair Campbell who had, he writes, "great clanking balls". But it was the row over then BBC reporter Andrew Gilligan's claims that the Iraq dossier had been sexed up that caused the relationship to deteriorate. "I had, insensitively and foolishly, not quite appreciated the strain Alastair had been under," Mr Blair writes. "He is, as I have said, a highly strung character." Elsewhere, he writes of Campbell reacting "like a mad axeman."

On public services, Mr Blair admits that the introduction of university tuition fees began with the "usual fraught exchanges with Gordon and the Treasury" and almost led to his resignation.

The lesson he draws from his reform programme is: "if someone isn't screaming somewhere, it probably isn't going to work". His advice to his successors is: "if you think a change is right, go with it. The opposition is inevitable, but rarely is it unbeatable. There will be many silent supporters as well as the many vocal detractors. And leadership is all about the decisions that change. If you can't handle that, don't become a leader."

Extracts: The thoughts of Tony Blair

Blair on Brown

“So was he difficult, at times maddening? Yes. But he was also strong, capable and brilliant, and those were qualities for which I never lost respect.”

“When it’s said that I should have sacked him, or demoted him, this takes no account of the fact that had I done so, the party and the Government would have been severely and immediately destabilised, and his ascent to the office of prime minister would probably have been even faster.... It is easy to say now, in the light of his tenure as prime minister, that I should have stopped it; at the time that would have been well nigh impossible.”

Blair on the Rev Ian Paisley

“He and I would often meet alone in the Downing Street den… we were both fascinated by religious faith as well as being people of faith. He gave me a little prayer book for Leo.

Once, near the end, he asked me whether I thought God wanted him to make the deal that would seal the peace process. I wanted to say yes, but I hesitated:though I was sure God would want peace, God is not a negotiator. I felt it would be wrong, manipulative, to say yes, and so I said I couldn’t answer that question, that only he could and I hoped he would let God guide him.”

Blair on Iraq

“I have often reflected as to whether I was wrong. I ask you to reflect as to whether I may have been right.”

“I still believe that leaving Saddam [Hussein] in power was a bigger risk to our security than removing him, and that terrible though the aftermath was, the reality of Saddam and his sons in charge of Iraq would at least arguably be made much worse.”

“I cannot regret the decision to go to war…. I can say that never did I guess the nightmare that unfolded, and that too is part of the responsibility.”

“I am now beyond the mere expression of compassion. I feel words of condolence and sympathy to be entirely inadequate. They have died and I, the decision-maker in the circumstances that led to their deaths, still live.”

Blair on New Labour

“I won three elections. Up to then, Labour had never even won two successive full terms. The longest Labour government had lasted six years. This lasted 13. It could have…gone on longer, had it not abandoned New Labour.”