Tennessee Williams could put it away. He died choking on a bottle cap, having worn away his gag reflex through years of alcohol abuse. Some of his greatest characters are drink-dependent: Blanche DuBois scurries bourbon bottles out of sight, Brick Pollitt throws back shots. His kinship with the sozzled barflies of Confessional should come as no surprise.

Dredged up for its British premiere by director Jack Silver, Confessional is the sort of writer's curio best left in the bottom drawer. A snapshot of a beachside bar in Southern California and its congregation of regulars, the one-act play is essentially a first draft of the far superior Small Craft Warnings, which came two years later.

Many of the characters return in that play, still stuck at the same bar, drinking the same drinks and playing the same string concertos on the jukebox. Though Williams never inserted a plot per se - both plays are portraits of a place - Small Craft Warnings refines the relationships and focuses the mood. Confessional's still a tangle of tangled lives.

Williams' title says it all. Monk's Place is a parish; its watchful proprietor (Raymond Bethley), a good Samaritan who looks after his lost soul customers. They prop up his bar, but it props them up too. As beautician Leona (Lizzie Stanton) rants and rails, howling at the moon as much as the men around her, Monk repeatedly reigns her in. He sees the suffering beneath her boozing - today, being the anniversary of her brother's death. Stanton turns her inarticulacy into slurred poetry.

She's not alone. Gavin Brocker's preening male prostitute swans about like he owns the place, enticing queer passers-by with a look, while Rob Ostlere's cook Steve takes advantage of the mentally disabled Violet (Simone Somers Yeates). Monk ashamedly follows suit; even priests being sinners.

Abi McLoughlin's Doc, a fully-functioning alcoholic, sinks silently into her brandy, disappearing only to deliver a baby nearby – a wreckless act played as a casual call. Her eventual confession is the play's best moment; a rare instance of Williams writing with the utmost restraint. More often he tips into a kind of overblown beat poetry; overwrought expressions of sozzled rage and despair.

At best, Silver's semi-immersive revival makes a case for its modernity. Transposed to contemporary Britain, Confessional reflects the decay of jaded seaside towns. Though plastic Union Jacks hang from the bar, the place feels forgotten about. Where it glitches, however, is in the illegality of homosexuality - a pivotal point in the play.

Reviving Confessional occasions strong, characterful performances, but little more besides. It feels more like an acting exercise than a production with purpose. The audience perch on bar stools beneath dart boards and disco balls, and can even pop to Monk's bar for a beer, but though elegantly underplayed, the production rarely wrings out either mood or metaphor. It's flat as a lager left out for too long.

Confessional runs at the Southwark Playhouse until 29 October.