Sally Potter's comedy-drama The Party is an enjoyably misanthropic affair boosted by some very fine performances and a screenplay almost as caustic as that of Who's Afraid Of Virginia Woolf? Over its brisk 71 minute running time, all its characters reveal their darker sides. They're affluent and privileged types who appear to have the world at their fingertips but we quickly discover their capacity for backbiting as well as some of some of their most intimate and incriminating secrets.

The hostess, first seen in slow motion, close up and brandishing a gun, is politician Janet (Kristin Scott Thomas). She has just been made a government minister and is celebrating with some of her oldest, closest friends. Thatcher-like, she wants to show off her ability to hold high office but still attend to the catering. Her husband (a very gaunt looking Timothy Spall) sits listening to blues and jazz while she busies herself in her apron in the kitchen. The first guests to arrive are Janet's old friend April (Patricia Clarkson) and her infuriating partner, lifestyle guru Gottfried (Bruno Ganz), who speaks only in New Age clichés. The other guests are lesbian academic Martha (Cherry Jones) and her dungaree-wearing lover Jinny (Emily Mortimer), who has just discovered she is pregnant with triplets. Also present is city slicker Tom (Cillian Murphy). He brings a gun and cocaine into the house but arrives without his wife Marianne (who works for Janet and who, even in her absence, plays a pivotal role in the plot).

Aleksei Rodionov's black and white cinematography gives the characters a sheen of elegance but their behaviour grows ever more barbaric. Potter's screenplay slowly reveals their bad faith and duplicity. They've been having affairs with each other. Illness, addiction and betrayal are clouding their lives. The fates are against them.

This is a chamber piece, clearly shot quickly and on a relatively modest budget. There is pathos as well as humour in the way what should be a celebratory evening so quickly unravels. Potter includes slapstick elements (a champagne cork shattering a pane of glass, Tom's attempts to hide his gun in the dustbin) but these sit aside moments of real bleakness. Amid the mounting mayhem, the writer-director finds the opportunity to throw in references to the creaking National Health Service, to feminism, class and workplace politics.

Potter strikes a very swift tempo. At times, the film grows as manic as Cillian Murphy's increasingly strung out Tom who needs a line of coke to help him cope with every social challenge the party poses him. One moment Kristin Scott Thomas's Janet is worrying about her hair and texting her lover. The next she is in a state of extreme angst and is declaring her undying love for her husband. In its mixture of jauntiness and despair, her performance here recalls the one she gave in Anthony Minghella's film version of Samuel Beckett's Play. Spall is morose in the extreme while Ganz's equanimity in the face of every new misfortune becomes ever more irritating.

At times, The Party becomes a little glib. The hidden connections between the characters are easy to spot and we can predict precisely who's at the door at the film's delirious endpoint. This, though, is lively and invigorating filmmaking with an energy that belies its own pessimism.

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