Nobody imagined that last autumn’s Netflix series Beckham was a warts-and-all confessional. “There were some horrible stories that were difficult to deal with,” said David, alluding coyly to reports in 2004 that he’d done the dirty with Rebecca Loos, not named in the film. “It was the first time that me and Victoria had been put under that kind of pressure in our marriage. Ultimately, it’s our private life.”

This new book from renowned investigative journalist Tom Bower exists simply to say: “No, it isn’t.” Forget the summer-hazed scenes of amateur beekeeping and opening up about OCD: Bower’s top line is that we should see David as a tax-avoiding serial shagger who was never even that good at football – and as for Victoria, she’s a talentless nonentity who’d probably be divorced if she didn’t need to monetise their marriage and feed her addiction to the limelight.

Such is the gist of this hilariously bitter book, best understood as a silent howl of rage for the litigation-muzzled dogs of Fleet Street; Bower might as well have scrawled “not fair” in crayon when he tells us that Beckham’s lawyers put paid to the Sun’s interest in a long-lens snap of him on the Med with “a beautiful unnamed blonde” in his lap.

As a tale of dosh and sex, the emphasis is firmly on the latter. Bower tries gamely to nose his way through the cul-de-sacs of Beckham’s accounts, truffling through earnings and investments in Madrid, Miami and Dubai, but the best he has on the tax stuff simply recycles a seven-year-old scoop in Der Spiegel, when hacked emails revealed the extent of Beckham’s ire once concern from HMRC nobbled his longed-for knighthood (“unappreciative cunts”).

The book’s main purpose is to piggyback on the Netflix doc while spewing all over it the regurgitated contents of every tabloid story ever to print Beckham’s name beside that of another woman, whether decades-old tabloid kiss-and-tells or nudge-wink gossip about him attending parties with models Helena Christensen and Bella Hadid. “True or not, the report was damaging” is the kind of formulation Bower appears to favour, which muddies the waters somewhat. Kate Beckinsale was “suspected of getting too close to David, although no evidence ever emerged”. Beckham and Charlize Theron “barely took their eyes off each other” at the draw for the 2010 World Cup. He’s even been “at parties where others enjoyed cocaine”, which no journalist would ever do.

Even if you think celebrities are fair game, The House of Beckham fails on its own grubby terms, because it’s all old news. I’ll admit that when I first heard of this book I was cynically wondering what skeleton in the closet might have made Beckham queue so long to see the Queen in pre-emptive atonement. But fresh dirt is conspicuous by its absence, despite Bower vaunting the “previously untold aspects of this extraordinary story” – which are what, exactly? Of more than 1,000 endnote references, all but four point to sources in the public domain (overwhelmingly, old tabloid tales) and of those four “confidential sources”, well… One of them is used to stand up a quote that Victoria’s early dress-making relied on “fabrics, seamstresses and pattern makers” from the designer Roland Mouret – which is something Vogue reported in 2008 after, er, her own PR team put it out. Another source informs Bower that Beckham, filming his first ad in 1997, was “quiet. There was nothing polished about him at all” (hold the front page). Another confirms that Beckham once advertised fish fingers: hardly a clandestine activity, by definition.

Those fish fingers really bother Bower. “As a child, announced the advertisers, Beckham had eaten fish fingers. That was disputable. Neither Beckham nor his mother had ever mentioned him eating that particular food.” The lying bastard! He once said he didn’t use a body double in a Guy Ritchie-directed H&M ad – but he did! Visiting Victoria in hospital after his third son was born, he drank Coca-Cola, “despite being paid to promote Pepsi”! In the end, Bower has to resort to telling us three times over that, by agreeing to become an ambassador for Qatar’s World Cup, Beckham “ignored its funding for Hamas”.

Beckham exploited his appeal to gay men, “big spenders on underwear”, says Bower, nothing if not a man of the world. His fame apparently stems from our “nostalgia for a tattooed lad enjoying his manly bravado” – what? – yet he and Victoria failed to comprehend that “there was a limit to the public’s fascination with two aspiring people from Essex” – a tin-eared self-own if ever there was one.

Bower isn’t incapable of conjuring a nicely feline phrase capturing the absurdity of his subjects’ lives (“On one critical matchday he was in London having dinner with Geri Halliwell after another miserable attempt to relaunch Findus”), but for the most part his writing is ludicrously bad here: “Famous among music fans as a June weekend of drink, dance, dalliance and a great deal more, David Beckham was enjoying three days of hectic partying at the Glastonbury festival.” That chapter ends with the suggestion that the Beckhams were there in 2017 to cynically stage their coupledom for the press – but when he says “rekindling memories of the Darkness in 2003 was forbidden”, he means Rebecca Loos, not Justin Hawkins opening the Pyramid stage.

A failure of research and craft, it’s also a failure of humanity. He’s constantly needling Victoria, “never the prettiest”, for her acne and “Cuprinol tan”, for how it was intolerable to be among other players’ wives, “many better looking than her”. “Few men would have resisted Rebecca Loos,” Bower writes. I shudder to imagine just how much pleasure he got from solemnly reporting that, in 2003, Victoria was voted “the world’s best-dressed woman for the second year running” – by readers of Prima. It’s ugly stuff: the reunited Spice Girls might have been renamed the Geriatrics because they were “all over-30 mums with boob jobs”. No doubt Bower would say Victoria plays the press, but never does he pause to reflect that she’s operating in a world in which a guy nudging 80 years of age can feel securely on the high ground peddling innuendo about eating disorders.

Bower, whose previous subjects include Gestapo officer Klaus Barbie and the fraudsters Robert Maxwell and Conrad Black, is absurdly unreflective here. He recounts how Andy Coulson, then editing the News of the World, “relying on a variety of sources” (lol) was “fired up against the Beckhams still selling the image of their happy marriage”. Coulson, another Essex lad who coincidentally happened to be cheating on his own wife at the time he broke the Rebecca Loos story, was later jailed for conspiracy to hack phones; Neville Thurlbeck, the reporter who brought him the scoop, was also jailed; as was the story’s broker, Max Clifford, later imprisoned for sex offences. Bower tells us that Coulson’s team celebrated an early splash with a knees-up in Mayfair: “First editions of the newspaper had long been on sale outside King’s Cross station when the celebrating journalists staggered into the dawn.”

That kiosk doesn’t even sell newspapers any more; meanwhile, Beckham’s dog has a devoted following on Instagram. I might, instinctively, have found that cause for regret, somehow – but then I read the petty, nonsensical, slipshod crap Bower gives us here. Then again, it probably isn’t meant for anyone but the Beckhams themselves, as a kind of bad-minded re-edit of the Netflix film, left gift-wrapped on the door of their $5m Burj Khalifa condo. When Bower devotes a paragraph to reciting the testimony of a Bosnian woman who claimed to have slept with Beckham five times in 2007 – “utterly untrue”, Bower adds – it can be there for no other reason than to annoy them. It’s the trajectory every investigative hack dreams of: start by writing about fugitive Nazis, end by trying to piss off Victoria Beckham.

• The House of Beckham: Money, Sex and Power by Tom Bower is published by HarperCollins (£22). To support the Guardian and Observer order your copy at guardianbookshop.com. Delivery charges may apply