First Night: God Of Carnage, Gielgud Theatre, London

Imagine the most supremely awkward social situation you can and multiply it tenfold. No, not today's state meeting between President Nicolas "Bling-Bling" Sarkozy, his new, erstwhile nude model wife and Her Majesty the Queen, but the nightmarish scenario cooked up by Yasmina Reza in her new play, God Of Carnage.

The Parisian playwright, who last year published an intimate biography of M. Sarkozy, has returned to Britain for the first time since 2000, hoping to emulate the phenomenal success of her 1994 play Art, which ran for eight years in the West End and took £150m worldwide. She has reunited with the same creative team of director Matthew Warchus and translator Christopher Hampton. Last night's star-studded audience was clearly willing her to succeed this time round too.

But however much they tried to roar with laughter at every possible opportunity and cheered on the heavyweight cast – Ralph Fiennes, Janet McTeer, Green Wing's Tamsin Greig and Art alumnus Ken Stott – it didn't shine, and not just because a power cut dimmed the lights half-way through, causing an unscheduled interval and the remainder of the show to be performed in the half-light.

The four-hander – played out on Mark Thompson's ominously blood-red set – portrays two sets of middle-class parents who hold a crisis summit to discuss a brutal playground fight between their respective sons. What begins as an agonisingly polite discussion over espresso and clafoutis (Reza excels at such fine details) rapidly deteriorates into a farcically awful, rum-fired slanging match.

The cast do try to give it their all. Stott has a pleasing moment when he rants and raves like a madman and McTeer as his bleeding-heart liberal wife – complete with faux peasant skirt, chunky beads, headscarf and wide-eyed sincere stare – is a wonderfully comic mixture of earthiness and brittleness.

Greig also explodes into life after a quiet start, deploying her considerable talent for (frequently unpleasant) physical comedy and showcasing a maniacal cackle. But Fiennes never convinces as Alain, her boorish lawyer husband. He is not, unlike the rest of the cast, a natural comic and his killer, bone-dry one-liners hit the mark only half of the time.

There are still gasp-worthy moments of rudeness as the characters switch allegiances, denigrating first their partners, then each other, and vie for attention like spoilt brats. But all too often in Warchus's confusing and stilted production these precious moments are lost.

This is Reza's nastiest play yet. She has proved she can skewer the middle classes like no other, stripping back the social niceties to reveal the grotesque prejudices and cruelty not only of her characters but also of the audience.

In the end, this curious hybrid of Who's Afraid Of Virginia Woolf? and Ayckbourn-esque farce left me feeling distinctly queasy.