Romeo and Juliet, Open Air Theatre Regent's Park, London

The night before the premiere of Timothy Sheader's Romeo and Juliet, I was watching I Vitelloni, the Fifties movie about spoilt, feckless young men in a grim northern Italian town. The next night, I thought I still was. Here again were the eager girls in circle skirts, the sulky boys combing their DAs, the carnival masqueraders doing the mambo. Here, too, was lots of background music – though not, unfortunately, by Nino Rota. And the whole thing had about as much to do with Shakespeare as did the Fellini film.

Sheader is a gifted director whose work I have enjoyed in the past, but his first production as artistic director of the Regent's Park theatre is a strained effort that puts music, dance, and design first, Shakespeare last. Not a single player in the colourless cast speaks with purity, passion, or panache.

In the name parts, Nicholas Shaw and Laura Donnelly are fresh-faced and wholesome looking. But the former's acting is pretty much limited to flashing a winning smile at the upper tiers, the latter's to waving her arms and exclaiming with breathy petulance. Claire Benedict's Nurse slumps around in a pinny cawing and cackling, and, when Oscar Pearce's Mercutio illustrates "the prick of noon" by placing her hand on his own, she squeals with delight; nor does she mind when he slaps her on the rump. She takes umbrage only when he pinches her breasts, making automobile-horn noises. As one might expect, such a Mercutio is a stranger to poetry – the Queen Mab speech is shouted in an offhand manner, with more emphasis on Pearce's running and jumping than on the evocation of the fairy world.

It might seem odd that, in this encounter with the rude boys, the Nurse wears a stylish gown and picture hat and is followed by a page staggering under a load of carrier bags, but no more so than the play's beginning with a slow-motion group grope (late Fellini, this). The actors disentangle themselves to inform us that, in Verona, "civil blood makes civil hands unclean", and, on the word "hands", thrust out their palms, as if showing mummy they have washed.

The two lovers easily find each other at the ball where, among guests in slutty or sinister red and black costumes, only they are wearing white. Despite the secrecy of the wedding, a dozen members of both families silently fling rose petals at the couple. In their underwear, they enact the bridal night on some wooden scaffolding outside the Capulet house while Juliet's family below plot to wed her to Paris. The two brawls, in which combatants take turns carefully rolling over each other's backs, are about as frightening as children's ballet, and, though Tybalt's and Mercutio's deaths are accompanied by plenty of gore, Juliet's (she shoots herself in the head) is sweetly bloodless.

When, after killing Tybalt, Romeo consults the friar, their lines are alternated with those of Juliet and her nurse in the scene that, conventionally, follows. One appreciates Sheader's wanting to speed things up, but the cross-cutting makes matters comical and confusing as the two young people wander distractedly about the stage, oblivious to each other, missing by inches.

So much, however, is a jumble – during the marriage ceremony a woman portentously sings "Ave Maria", but Juliet is so irreverent as to make the sign of the cross airily with the hand holding her bouquet. The meat of the play – love, fate, death – is constantly at odds with Sheader's frilly packaging. If swirly skirts and mambos are what he cares about, why didn't he just go the whole hog and do West Side Story?

To 2 August (0844 826 4242)