Gethsemane, National Theatre, London

A Cabinet minister's husband is due up in court for charges relating to his "innovative" overseas investment portfolio. The Home Secretary's rebellious child is caught smoking dope. The Labour Party's chief fundraiser, a flashy former pop impresario, rakes in cash via "chance" meetings over chilled white Burgundy.

Sound familiar? That's the point. Half the fun in David Hare's new play Gethsemane comes from spotting the political parallels – a Jowell jibe here, a Deripaska dig there. This is the third in a series from Hare, which began in 2003 with The Permanent Way, about rail privatisation, followed by Stuff Happens, about the run-up to the Iraq War.

Now Hare has turned to the thorny issue of party funding, the peg on which he hangs a wider debate between idealism and pragmatism. Oleaginous fundraiser Otto Fallon (Stanley Townsend) recruits the husband of an idealistic teacher, Lori (Nicola Walker), to help him pump the rich for cash. Across town, Meredith Guest, the Home Secretary, is flapping to cover up the misdemeanours of her teenage daughter, who is dabbling publicly in sex and drugs. Handily, Fallon happens to be a generous member of her school's board of governors; but, one cover-up successfully in place, Guest's dodgy husband comes under the spotlight.

Hare has drawn his characters with the broadest of brush-strokes: Fallon is a hairdresser-turned-mogul-turned-bigwig with ponytail and tasteless designer cardigans who has pulled himself up "from Hendon to Hampstead"; gimlet-eyed Guest, played with wonderful rigour by Tamsin Greig, is a career automaton who can't be alone with her daughter. The hip PM – a brilliant Anthony Calf – is found in full Boden gear, behind his drum kit in his Westminster basement den.

You know you're in a Hare play from the moment Lori walks out on stage, bathed in cool blue light, and gives her opening address. There are an awful lot of these moments, which, combined with the weird way Hare seems to think people talk – all repetitive tics and neat aphorisms – add up to an unsatisfying play that treads an uneasy line between docu-drama and fantasy. This is a world where rich men are uncultured oiks, politicians are inhuman and comprehensive school teachers are saints. Christmas has come early to the National – go along to boo and hiss at the biggest political panto in town.

To 24 February (020-7452 3000)