There was a fist fight between Alastair Campbell and Peter Mandelson in a Brighton hotel room shortly before Tony Blair was to deliver a speech to young Labour activists in February, 1995. A disagreement between the two men occurred and Mandelson screamed, “I’m sick of being rubbished and undermined, I hate it and I want out.” I’ll let Alastair take up the story: “He started to leave then came back over, pushed at me, then threw a punch, then another. I grabbed his lapels to disable his arms and TB [Tony Blair] was by now moving in to separate us and PM just lunged at him, then looked back at me and shouted, ‘I hate this. I’m going back to London.’ ”

Hilarious stuff, no? You may have thought Sebastian, the prime minister’s petulant, flouncing, homosexual aide from Little Britain, was a preposterous fictional creation, but I’m tempted to believe David Walliams and Matt Lucas had the inside track. Mandelson crops up in this book a lot, and it is rare for him to do so without stamping his little feet and screaming that he hates everyone and is going right home right now! Either that or depositing a stiletto deep between an absent colleague’s shoulder blades.

But the fight is more than yet another chance to laugh at Mandelson; it is, in its way, a perfect microcosm of the new Labour project – and not just the loathing, bitterness and paranoia that clings to all its leading progenitors. The cause of the fight tells you quite a lot about new Labour, too. It wasn’t a disagreement over clause four, or privatisation, or reform of the NHS. It occurred because Campbell and Mandelson could not agree what Blair should wear for his speech: Alastair wanted him to put on a suit and tie, whereas Peter thought he’d look nicer in some cords and an open-neck shirt. It is a cliché to say that new Labour was philosophically an empty vessel obsessed with surface; but we never knew to just what extraordinary extent that was true.

This is a riveting, compelling and genuinely revelatory book, although, paradoxically, there is little real “news” in it. This is because, ever tribally loyal, Alastair has removed anything which he feels might damage new Labour. So Blair’s language has been cleaned up, the sheer poison of his rows with Brown excised, the vendetta against the BBC (in which I should probably declare an interest, having been editor of the Today programme before the Andrew Gilligan affair blew up) toned down. Indeed, the whole Kelly-Gilligan business, about which Campbell is these days showing strange signs of contrition, had a certain horrible inevitability about it; an increasingly dyspeptic and desperate spin doctor losing control of public opinion and lashing out at a target (Gilligan) that had riled him for years. Heaven knows what else Campbell consigned to the bin, temporarily at least. The remarkable thing, though, is that he thinks that what remains isn’t damaging to Labour. It is, very.

Of hard fact, there’s little we didn’t know. We might be surprised that the prime minister was almost perpetually on the cusp of forcing Britain into the single-European currency; we might shudder at the time he considered making John Prescott foreign secretary. But this is small beer. Nor is there much in the way of general insight offered by Alastair himself. Here he is on Prince Charles – “something a bit sad about him . . . surrounded by luxury . . . people fawning on him, and yet somehow obviously unfulfilled”. And Princess Diana? “Absolutely, spellbindingly, drop-dead gorgeous.” Jacques Chirac? He’s “up himself ”. Bill Clinton? “A people person” and very good at communicating, apparently.

No, the pleasure of this book lies elsewhere, in the bile and hatred that seeps from every page. Man-delson v Brown; Cook v Reid; Cherie v Alastair, everyone v Clare Short; Alan Milburn in a “rage” that Brown had trampled on his territory and suggesting he be sacked forthwith. And, of course, Brown v Blair. For all Campbell’s self-censorship, the current prime minister is an unseen presence throughout, growling and sulking behind the arras. The sheer scale of the mistrust and open dislike between the leading players here leaves you surprised that they survived to the end of their first term of office.

Then there is that famous, obsessive, perhaps pathological need (on the part of Blair and Campbell) to control everything; to brook no argument, to shoehorn everyone and everything into a story line the two of them have written. This extended way beyond the cabinet and was at its most intrusive and emetic during the preparations for the funeral of Princess Diana. Campbell recalls: “I [also] felt it was important that Charles made some sort of gesture towards the boys, a touch, a hug, something that said father and son, not just royal family.” That they would not shrink from telling the heir to the throne to hug his kids for the sake of the cameras explains a certain frostiness towards new Labour from the royal family. The funeral proceeds precisely as Campbell and Blair wanted, the PM all moist-eyed and voice a-quaver at the lectern. And the following morning, Campbell notes, with quite extraordinary, inappropriate smugness: “Everyone was saying how well TB did yesterday and how badly Hague had done in his tribute to Diana. ‘People’s Princess’ was the phrase everyone was using.”

There is a sort of codeword used repeatedly by Blair and Campbell for those who refuse, usually out of principle, to toe the line. They are described as not being “serious”. An awful lot of people are afforded this description. Neil Kinnock for raging about Blair’s eulogising of Margaret Thatcher: “That woman f***ing killed people!” He’s not serious. Clare Short isn’t “serious”. The judgment “not serious people at all” is applied on one occasion to the whole cabinet. Journalists, en masse, are not serious (and frequently simply “scum”). Later still, as public anger at the war against Serbia gains momentum, we learn that the entire British people are not “serious”. Philip Gould’s focus group revealed a strong distaste for the fighting and the waste of money involved. Campbell notes: “It made you wonder why we bothered sometimes. PG said he wanted to hit some of them.” It makes me wonder why they bothered, too, frankly.

Campbell’s vitriolic hatred of the press was perhaps occasioned by his relentless, obsessive need to curry favour with it. Alongside each splenetic diatribe about the sewer-dwelling hacks who demean politics with their “culture of denigration” are the most extraordinary examples of brown-nosing editors and executives, of sheer jubilation when for example David English (then the chairman of Associated Newspapers) says Blair is doing a pretty good job, of the quite enormous lengths they went to get Rupert Murdoch’s support. It is but one example of the inherent corruption of the Blair regime that Campbell would dole out stories – ie policy announcements – to favoured journalists as a kind of pat on the head, or simply to spite more difficult rival hacks. “I gave it to The Sun to f*** The Mirror,” etc, etc.

The Campbell that comes across in these diaries is certainly a complex and interesting character; almost always angry, almost always depressed, wreathed in self-pity and self-justification. A flat-track bully occasionally gripped by the most maudlin sentimentality. But also engagingly frank, with a winning line in black humour, a certain blokeishfaux-naivety when faced with an array of international statesmen and an unrivalled understanding of how the tabloid press works. He was himself, of course, an average-to-good tabloid political journalist, accustomed to seeing the world in a Manichean split of black and white. But the notion of journalism being a trade wherein wrongdoers can be brought to account, where light can be shed into the darkest areas simply for the benefit of revealing a certain truth, is quite alien to him. And that is the problem, was the problem, perhaps, with new Labour: its utter disregard for the truth, the whole truth and nothing but the truth. For Campbell, if the truth doesn’t fit, then change it. Or miss bits out. Truth in the end is nothing more than a political commodity. Avoiding telling the truth is perfectly acceptable if it prevents a sudden slide in the opinionpolls. All political parties behave this way to some extent, I suppose – but most see it as a rather shady means to an end. For new Labour, it seems to have been an end in itself.

It is much as Kinnock had it, during that rant about Blair’s praise for Thatcher. Speaking about Blair in mid1995, he said: “Tax, health, education, unions, full employment, race, immigration, everything, he’s totally sold out. And for what? What are we FOR?” But then Kinnock – well, he’s not a serious person.

THE BLAIR YEARS: Extracts from the Alastair Campbell Diaries by Alastair Campbell
Hutchinson £25 pp794
Buy the book here at the offer price of of £22.50 (inc p&p)

Times Recommends

• The Sunday Times 100 best holiday reads
• What will we be reading this summer: the booksellers predict
• Literary festivals: a survivor’s guide