The arrival in Paris of rich widow Hanna Glawari sets the cat among the diplomatic pigeons at the Pontevedrian embassy, as they try to prevent her - and her F20m fortune - falling into French hands. Cue shenanigans in sheds, ethnic dancing, the taking off of trousers and the losing of fans.

John Copley's new production of Franz Lehár's The Merry Widow for English National Opera is as snazzy as can be, both costume (Deidre Clancy) and set (Tim Reed) playing up the jokes inherent in belle époque Paris and "a backward Balkan state" without excessively taking the mickey. Oliver von Dohnanyi and his orchestra likewise carry off ballroom zest and rustic folk song with equal flair. The singing (and speaking) is uniformly excellent. Amanda Roocroft (Glawari) is wonderfully flirtatious and very easy on the eye for a lady of . . . her years. Woodstock resident Alfie Boe (Rosillon) and Richard Suart (Baron Zeta) make a perfect ironic duo of the lovelorn cad and the blustering cuckold, respectively. Roy Hudd is superb as Njegus, the capering David Hemmings-alike flunkey.

John Graham-Hall steals it, though, as the dissolute Count Danilowitsch - "to diplomacy what the guillotine is to sore throats" - a determined bachelor, resolute non-dancer, and frequent flyer chez Maxim (a house of negotiable repute).

And yet . . . somehow The Merry Widow contrives to be less than the sum of its parts. The music is a chaotic patchwork of borrowings from Puccini, Bizet, Dvorák, Tchaikovsky and others, resulting in a kind of two-hour Fantasia: something GCSE students might have created if given a Classic FM Best of 19th-century Opera box-set, and told to make their own. It's neither Verdi nor G&S, nor anything distinguishable in between. Nor is it evidently a spoof on opera itself.

The libretto and score take turns letting each other down. With few decent - or even indecent - laughs, it's not consistently funny enough to be comic, and most of the attempts at hilarity degenerate swiftly into panto-level campery involving tasselled hats. The third act collapsed completely into a gay Parisian Last Night of the Proms. Brilliantly executed, to be sure; but just wrong, wrong, wrong. And there's far too much dancing, which, unless you go for prat-falls, severely limits the scope for humour. Imagine Onegin with jokes.

Just before the 1905 premiere, Lehár's Viennese management got cold feet over his musical melange and slashed the production budget, forcing the show to open with second-hand Japanese' scenery. If it had been my money, I reckon I'd have done the same.

The Merry Widow just isn't a particularly good opera. Nothing very wrong with it, but nothing much right, either. So three stars for ENO - but bronze ones, I fear.

The production continues at the Coliseum, in Londin, until May 30. Box office: 0871 911 0200 (www.eno.org).