Mexico is a state in crisis, as drug-fuelled crime spirals and murder rates match those of nations at war. The narcotic cartels rule their domains with virtual impunity, the only real challenge to their domination lying in possible new combinations of rivals and institutions. They eat their own. Meanwhile, the cowed populace becomes inured to horrific violence as the entirely innocent die as frequently as those who know they're headed to hell.

No wonder this vibrant yet troubled country has become a favourite subject of artists and writers and filmmakers, eager to explore its complex and maybe prophetic situation. Now Oliver Stone follows in the steps of heavyweight thinkers like Roberto Bolaño with a subtle and nuanced study of how transnational criminal organisations are corrupting society on both sides of the notoriously porous US-Mexican border.

Only kidding. Few things are funnier than an unintentional comedy, and Stone's gloriously ill-judged adaptation of Don Winslow's popular thriller is so delightfully clumsy that Showgirls-level cult status surely beckons. Honestly, if John Waters was let loose on an action movie it wouldn't be as camp as this.

After an hour of the press screening I attended, the humour dam broke and the crowd of seasoned blaggers started to giggle out loud. Maybe it was Benicio Del Toro's turn as Nick Cave trying to channel Charles Bronson's grumpy soul, or Salma Hayek's inexplicable Jessie J hairpiece (dramatically removed at one moment of emotional crisis) or the similarity of Aaron Johnson's neck tattoo to a kiddies sketch of a turd, but once the scales fall, this idiotic film is rather diverting.

The realisation that an experienced cast are actively refusing to be directed certainly makes for entertainment. Hayek, as a Mexican crime queen, plays it as pure telenovela from the start. Del Toro, as her disloyal lieutenant, obviously ordered to use a physical twitch to signify lying, simply tries to tear off his moustache, possibly in despair.

Meanwhile, their gringo counterparts thesp it up in various ways. John Travolta, looking uncannily like Neil Innes these days, is oddly uncommitted as a corrupt federal agent. The unfortunately named Taylor Kitsch - the Lidl Matt Damon - as a disturbed veteran shows yet again that, just as the US never learns from its pointless foreign adventures, its acting corps never learns how to portray a convincing ex-soldier. Just how bad are they at wars that they all come back as psychos?

Still, it means his character, the oddly named Chon, knows how to wield a shooter and where to find unemployed men with firearms experience when the moment comes. Along with his schoolfriend Ben (Johnson), he runs a touchy-feely marijuana growing corporation who specialise in weed that's high in THC, the sort of stuff that gives teenagers brain damage. But as they buy water pumps for the Third World with the cash that the IRS never hears about and drive an electric Tesla (which certainly rules out any long chase scenes), they're respectable - the Waitrose of drug barons.

Losing political protection at home, Elena (Hayek) takes her cartel business up North and, seeking a quick way in, strong-arms Chon and Ben's mom and pop dope corporation and kidnaps their mutual squeeze, the ghastly Ophelia, a lost rich girl who smokes weed and eats salad (eh?). She's so convincingly played by Blake Lively I was screaming "KILL HER! KILL HER NOW!" each time her abductors dropped a pizza by her primitive cell.

Cue shootout, revenge and absurdity, badly handled right to the end. The Mexicans are all shiftless and badly dressed, the single African-American character fucks up his sole task, and the invaders from below the border are successfully routed by the WASP-y heroes. Take that, you greasy wetbacks! America is proud of its marijuana farmers!

Still, such casual racism is not even the worst fault of this perfect shambles. The script, the tone, the acting, the direction - they're all weak, offering plenty to dissect. And there are some casual gags that may even be deliberate, such as giving Lively's character a Sex And The City voiceover role à la Sarah Jessica Parker, then making her travel in a horsebox. Savages may be atrocious, true, but at least it's not boring, and it is much funnier than Pineapple Express.