Private Lives, Vaudeville, London<br/>A Day at the Racists, Finborough, London <br/>Moonfleece, Rich Mix, Shoreditch, London

Framed in gold, the scene is like a religious icon, only one that exalts deluxe hedonism. Lolling in silk dressing gowns on a huge velvet ottoman, Kim Cattrall and Matthew Macfadyen are the old flames, Amanda and Elyot, in Noël Coward's comedy Private Lives. "Wow!" breathed the woman behind me, readily seduced as the curtain rose on this gilded vision in Act II of Richard Eyre's new West End staging.

If briefly stunning, alas, Rob Howell's set designs soon seem rather ghastly. Amanda's flat in Paris – where she and Elyot are ensconced, having given their second spouses the slip – resembles some exotic mausoleum. It's a domed chamber, drenched in gilt, with one small, shuttered window high up in the wall.

Perhaps Eyre wanted to suggest claustrophobia with this hermetic bolt-hole, where Amanda and Elyot swerve back and forth between smooching and blazing rows. Even in 1930, when Private Lives premiered, one critic spotted how this farce flirted with tragedy in portraying a couple who can't live with or without each other. Moreover, since the NT's 2007 production of Present Laughter (where the gaiety was punctuated by wireless reports of the Nazis' rise), the urge has been to find more dark anxieties in Coward's comedies, without destroying their scintillating wit.

That fine balance remains elusive here. Macfadyen picks up on the sour and bullying streak in Elyot, yet he offers few compensating qualities. With no flashes of raffish humour in his glazed eyes, he comes across as a boorish stuffed shirt. Even in silk, he lacks swish. Indeed, one wonders if he mightn't have been better cast as the stolid Victor, whom Amanda has ditched at the honeymoon hotel in Act One.

Macfadyen has one genuinely touching moment – charged with desire and long-term affection – when he gives Amanda's negligee a little yearning tug as she brushes past him, heading for another swig of brandy. Elsewhere, the sexual chemistry isn't there.

Cattrall demonstrates more flair for physical comedy, flinging herself on the ottoman with wonderful, petulant abandon. Unfortunately, straining to sustain an upper-crust English accent, she delivers many of her speeches in a monotonous sing-song. Though luminously beautiful, she hardly delves below the surface emotionally.

Still, the joy of Coward revivals is that his repartee sounds surprisingly fresh, naturally sparky. There's also fun to be had when Cattrall and Macfadyen tussle furiously, trashing the pied-à-terre. Skewered, a fancy goldfish bowl spews water over Simon Paisley Day's Victor, who has tracked down Amanda at last.

In the end, it is he who outshines the rest, briefly managing to be both absurd and pained, teetering on the brink of a stuttering breakdown as he attempts to maintain polite small talk, nibbling on a brioche amidst the debris.

The real "wow" of the week is A Day at the Racists by Anders Lustgarten, a political activist turned breathtakingly confident playwright. As general election campaigning kicks off, several fringe theatres are tackling the issue of how the BNP is attracting voters. While still in rehearsal, these productions have also, apparently, been taking the flak of neo-fascist slurs and threats. The police are, I'm told, ready for a rapid response in case any trouble flares up at the Finborough.

A Day at the Racists is set in Dagenham where Peter (Julian Littman), a burly, white working-class, erstwhile Old Labour devotee, is disillusioned. Enraged, he sees the state as favouring new immigrants while his son Mark – a single dad – sleeps on Peter's sofa and struggles to find work, with no hope of a council flat. Peter is drawn in by the rebranded, suit-wearing BNP – in this case slightly futuristic with an avid British-Pakistani candidate (Thusitha Jayasundera) on its books.

The strength of Lustgarten's drama is that his central characters – family, old mates and new lovers; white, black and mixed race – all engage your sympathy and voice their arguments passionately, even as they struggle with confused ideas of Britishness and complex private motivations.

This low-budget staging is a little rough around the edges. Nonetheless, Ryan McBryde's production is terrifically fluid, with gripping performances from almost everyone. Littman's face-off with his appalled son (excellent Sam Swainsbury) is searing, and Nick Holder is chillingly diplomatic as Rick, a racist yob turned spin-doctor.

A Day at the Racists is more than a match for Richard Bean's NT satire, England People Very Nice, and better than some of David Hare's state-of-the-nation plays. Unfortunately, Philip Ridley's Moonfleece is feeble by comparison. Its premiere is timely enough, opening in the East End, then touring to Bradford and elsewhere. Moonfleece also sets out to explore why underprivileged white Britons might canvass for the far right. But Ridley's scenario just ends up being embarrassingly fanciful. Neo-fascist youths in suits, bearing election leaflets, invade a gay couple's squat for a meeting that turns into a seance-going-on-storytelling session. Curtis (Sean Verey) thinks his step-dad, the candidate Mr Avalon, is sound, until the fairy tale told lets him see that he is really a wicked homophobe, who sent packing Curtis's beloved gay brother.

David Mercatali's young cast, for the troupe Supporting Wall, do their best, and Sian Robins-Grace enjoys herself as the frisky spiritualist Nina – surely a warm-up for Noël Coward's Blithe Spirit. Too bad the promised fairy tale turns out to be so dismally predictable.

'Private Lives' (0844 412 4663) to 1 May; 'A Day at the Racists' (0844 847 1652) to 27 Mar; 'Moonfleece' (020-7613 7498) to 13 Mar, and touring

Next Week:

Kate Bassett tests her own and Andrew Lloyd Webber's powers of endurance with Love Never Dies, his sequel to The Phantom of the Opera