We are treated to one of George W Bush's infamous turns of phrase, taken from a campaign speech in 2000, when he proudly declared, "Families is where our nation finds hope, where wings take dream."

This unintentional verbal faux pas surpasses anything in McKay and Will Ferrell's script, which is as gleefully mean-spirited as it is unnecessarily foul-mouthed.

The flimsy premise reunites Ferrell and John C Reilly, who co-starred in Talladega Nights: The Ballad of Ricky Bobby, as 40-something men who possess the mental age of adolescents.

Forced to live together, these two idiot savants – with the emphasis on idiot – bicker incessantly before realising the error of their ways. Brennan (Ferrell) is 40 years old going on 14. He still lives at home with his mother Nancy (Mary Steenburgen).

During a medical convention, Nancy meets Robert (Richard Jenkins), who has his own adult son at home – Dale (Reilly) – and they embark on a whirlwind romance. Wedding bells peel and Nancy moves in with her new husband with disgruntled Brennan in tow.

The living arrangements pose a dilemma because for the first time ever, Dale must share his bedroom.

Sibling resentment boils over with Dale's cherished drum kit taking the brunt of the frustrations, but the stepbrothers unexpectedly discover common ground: favourite dinosaurs and their shared hatred of Derek.

When Dale subsequently discovers his stepbrother's gift for singing, they suddenly find their direction in life as a musical double-act.

Step Brothers is just as scatological, messy and puerile as Anchorman and Talladega Nights, and will therefore delight audiences who lapped up Ferrell's buffoonery in those pictures.

If the lead characters were likeable, or their childish behaviour in any way comprehensible, then we might feel compelled to chuckle occasionally. Instead, when a gang of pint-sized playground bullies beats the gruesome duo to a pulp, we strongly resist the urge to cheer.