By the time Clare Short left the Cabinet last year, she had managed to exasperate many of her friends as well as her enemies. But, she tells Nick Morrison, she doesn't regret not resigning.

WHAT would have been surprising is if Clare Short had gone to sit quietly on the backbenches after leaving the Cabinet. After all, she has spent most of her political life failing to keep her mouth shut. Even then, however, the ferocity and persistence of her attacks on her former colleagues have caused much sharp intaking of breath.

In the 18 months since her resignation, she has become something of an Ancient Mariner, stopping everyone who will listen to tell them of the Government's, and specifically Tony Blair's, failings. She calls for his resignation on a regular basis. She is not a woman who gives up easily.

"A lot of people say it has happened and we have got to brush it under the carpet and go forward, but Iraq is a big mess and it is not going away and it is wrong to brush big errors under the carpet," she says.

"We have got to learn how such errors came to be made, to put them right. It is for the historians to write history, but if you are in a mess you need to understand how we got there and how we get out of it."

Not content with a verbal onslaught, she has now put it in print. An Honourable Deception? covers the ups and downs of the Blair government but, as its name suggests, it pays particular attention to the build-up to war in Iraq and its aftermath. It is not an account which portrays the Prime Minister in a favourable light.

Her contention is that Mr Blair decided it was right to support the US invasion of Iraq, and was prepared to mislead both his Cabinet colleagues and the country to get there, the honourable deception of the book's title.

"Tony Blair undoubtedly engaged in a series of half-truths, deceptions and exaggerations to get us to war. It is clear that he gave his word to President Bush, he was not straight with Parliament or the country," she says.

'Presumably, he thought that was an honourable thing to do. Presumably, he thought that was the right thing to do."

But the betrayal was more personal than that. As a prominent left-winger, she was a key figure for many in the Labour Party: if she could support the Government, so could they.

The result was that the Prime Minister went to extraordinary efforts to keep her in the Cabinet during the build-up to war.

"I kept saying we must move on the road map to a Palestinian state and we must go through the UN to be serious about resolving the problems in Iraq. Tony kept saying yes, yes, yes," she says.

In the end the bid to get a second resolution was ditched, again under a false premis, this time that the French would veto any resolution, and the road map in Palestine proved to be worthless.

As International Development Secretary, Ms Short was privy to much of the intelligence information on Iraq's supposed WMD, information which showed the Government's claims had been vastly exaggerated. Knowing the case for war was tissue-thin, she decided to stay in the Cabinet. It must have been flattering to have the Prime Minister spend so much time assuaging your concerns.

"I was going to leave the Government because of the rush to war, and Tony Blair pleaded with me to stay and promised me two things: to get President Bush to announce the road map and to internationalise the reconstruction of Iraq.

"I took a lot of flak but he didn't mean all that. He didn't stick by it. Clearly he just said those things to get me to do his bidding at the time."

Presumably, it is this feeling of being conned which motivates her refusal to let go. And it's hard not to think she doesn't sometimes regret not quitting earlier, or at least regret being taken in.

Her decision to stay drew considerable criticism from her natural supporters. By contrast, former Foreign Secretary Robin Cook's resignation in the build-up to war saw his standing rise among the left.

When she did finally quit, over the issue of the lack of a role for the UN in rebuilding Iraq after the war, it was too late to restore her reputation. And her usefulness to Mr Blair over, there was little effort this time to persuade her to stay.

But she insists she was right not to resign earlier.

"I'm still glad that I tried. If I had left at the same time as Robin Cook I would have thought 'Could I have made any difference?'. Some people tell me I should have handled things differently, as though they're giving me careers advice," she says, testily.

In her book, she claims that involving the UN in the reconstruction work "would have brought progress to the Middle East, eased the division in the world and prevented the growth of al Qaida," but this seems somewhat nave - it is surely the invasion and occupation itself, rather than the lack of Belgian and French companies in Iraq, which is proving the sore point.

To Ms Short, the Government's policy on Iraq is an example of the way decision-making has been passed to a small group of people, the Prime Minister and close advisors, bypassing Cabinet altogether. Not only is this system undemocratic, but it is prone to making errors, she says, in Iraq's case of monumental proportions.

"The question for all of us is do we want to live in a political system that works like that? To have a leader who makes a decision and is not truthful with the country and the Cabinet?," she asks.

Even before Iraq, she had begun to feel uncomfortable in a Blair Cabinet, as the successes of the first term: low unemployment, minimum wage, tax credit, gave way to the mistakes of the second: top-up fees, foundation hospitals, and now casinos. "I'm very sad about what has happened to my Government. I don't take any pleasure in these aspects that have gone so wrong," she says.

Before Iraq, she had gritted her teeth and tried to keep out of the way, concentrating on running her department, which secured an international reputation and is one of Labour's few real success stories. Does she miss it?

"Obviously," she says, sadly. "It was very fulfilling, a very fine organisation. I was very sad to leave it, no question."

But she says she doesn't yearn for power or its trappings, including the Government car.

"The car? I don't see that. You don't walk, you don't see people, you get unfit, you go to too many dinners, you put on weight. That is not a very good lifestyle," she says, allowing herself a laugh.

"It might make people feel important but it is not good. I don't miss the car at all. I had a very good driver, though. Chris. I see him occasionally."

Her latest resignation was the third time she quit the Labour frontbench - the first time over the first Gulf War and then over the prevention of terrorism laws - but this time she sees little prospect of a recall, although she doesn't seem at all dismayed by that.

"It is extremely unlikely, but if it happened to me the offer would have to be something I really wanted to do to make the work you have to do worth it," she says.

In the meantime, she is going to carry on calling for the Prime Minister's resignation. "It is a question for the people of Britain to put pressure on Tony to do the honourable thing. I still think that would be the best outcome," she says.

Although she is warmer in person than she often appears, she seems to have more anger than is good for a person, but then she has a lot to be angry about: the world is in a mess, the country was misled, and she has been duped.

It's the anger in her politics that means you know she's genuine, and it's the anger that means you know she's not going to leave the Prime Minister alone until he quits. Is she ever going to let it go? There's no keeping the scorn from her voice.

"You are supposed to just say it once and then you have said it? The point is the crisis is not resolved. I'm not saying it for the sake of it."

* An Honourable Deception? (Free Press) £15.